JP6734890B2 - Method for treating titanium alloy - Google Patents

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT This invention was made with United States Government support under NIST Contract No. 70NANB7H7038 awarded by the National Institute of Standards and Technology (NIST), US Department of Commerce. The US Government may have certain rights in this invention.

The present disclosure relates to methods for treating titanium alloys.

A method for producing titanium and titanium alloys having a coarse grain (CG), fine grain (FG), fine grain (VFG), or ultra fine grain (UFG) microstructure is disclosed using multiple reheating and forging steps. including. The forging step may include one or more upset forging steps in addition to draw forging in free press.

As used herein, when referring to the microstructure of a titanium alloy, the term "coarse grain" refers to an alpha particle size of 400 μm or less to greater than about 14 μm, and the term “fine grain” refers to 14 μm or less to greater than 10 μm. The term "fine particles" refers to an α particle diameter of 10 µm or less to more than 4.0 µm, and the term "ultrafine particles" refers to an α particle diameter of 4.0 µm or less.

Known commercial methods of producing titanium and titanium alloys to produce coarse or fine grained microstructures use multiple reheating and forging steps to produce 0.03 sec ^{−1 to} 0.10. A strain rate of sec- ¹ is used.

Known methods intended for the production of fine-grained, fine-grained, or ultra-fine grained microstructures apply a multi-axis forging (MAF) process at ultra-low strain rates of 0.001 sec ^-1 or less ( See, for example, G. Salishchev, et. al., Materials Science Forum, Vol. 584-586, pp. 783-788 (2008)). A typical MAF process is, for example, C.I. Desrayaud, et. al, Journal of Materials Processing Technology, 172, pp. 152-156 (2006).

The key to the grain refinement in ultra low strain rate MAF process, ultra-low strain rate to be used, i.e., the result of 0.001 sec ^-1 or less of strain rate, continuously in system dynamic recrystallization The ability to work. During dynamic recrystallization, the grains simultaneously nucleate, grow and metastasize. The occurrence of dislocations within the newly nucleated grains continuously reduces the driving force for grain growth, and grain nucleation is energetically favorable. The ultra low strain rate MAF process uses dynamic recrystallization to continuously recrystallize the grains during the forging process.

Relatively uniform cubes of ultra-fine grained Ti-6-4 alloy (UNS R56400) can be produced using the ultra low strain rate MAF process, but the cumulative time required to perform the MAF step is May be overkill in a commercial setting. In addition, conventional large-scale commercial free-press forging equipment may not have the ability to achieve the ultra-low strain rates required in such embodiments, and thus custom-built forging equipment may It may be needed to perform production scale ultra low strain rate MAF.

Thus, it does not require multiple reheats, provides higher strain rates, reduces processing time, and/or eliminates the need for bespoke forging equipment, coarse, fine, fine grain, It would be advantageous to develop a process for producing titanium alloys with ultrafine grained microstructure.

According to a non-limiting aspect of the present disclosure, a method of refining a grain size of a work piece comprising a titanium alloy comprises beta annealing the work piece. After β-annealing, the workpiece is cooled to a temperature below the β-transus temperature of the titanium alloy. The workpiece is then multi-axis forged. Multi-axis forging involves forging a workpiece within a workpiece forging temperature range in the direction of a first orthogonal axis of the workpiece at a strain rate sufficient to adiabatically heat the interior region of the workpiece. Press forging at a temperature and at a strain rate sufficient to heat the workpiece adiabatically to the interior region of the workpiece, in the direction of the second orthogonal axis of the workpiece, within the workpiece forging temperature range. Press forging at the workpiece forging temperature, and forcing the workpiece at a strain rate sufficient to adiabatically heat the interior region of the workpiece in the direction of the third orthogonal axis of the workpiece at the workpiece forging temperature. Press forging at a workpiece forging temperature within the range. Optionally, during the successive press forging steps, the adiabatically heated interior region of the workpiece is allowed to cool to a temperature at or near the workpiece forging temperature within the workpiece forging temperature range, and The outer surface region is heated to a temperature at or near the workpiece forging temperature within the workpiece forging temperature range. At least one of the press forging steps is repeated until a total strain of at least 1.0 is achieved in at least one region of the workpiece. In another non-limiting embodiment, at least one of the press forging steps is repeated until a total strain of at least 1.0 up to less than 3.5 is achieved in at least one region of the workpiece. In a non-limiting embodiment, the strain rate used during press forging is in the range of 0.2 sec ^{-1 to} 0.8 sec ^-1 .

According to another non-limiting aspect of the present disclosure, a non-limiting embodiment of a method of refining a grain size of a workpiece including a titanium alloy includes beta annealing the workpiece. After β-annealing, the workpiece is cooled to a temperature below the β-transus temperature of the titanium alloy. The workpiece is then multi-axis forged using a sequence that includes the following forging steps.

The work piece undergoes a major reduction at a work piece forging temperature within the work piece forging temperature range in the direction of the first orthogonal A-axis of the work piece at a strain rate sufficient to adiabatically heat the interior region of the work piece. Press forged to the spacer height. As used herein, the major reduction spacer height is the distance corresponding to the desired final forging dimension for each orthogonal axis of the workpiece.

The workpiece has a first roughing reduction spacer height at a workpiece forging temperature within a workpiece forging temperature range in a direction of a second orthogonal B axis of the workpiece under a first roughing pressure. ) Is press forged. The first blanking reduction is applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the first roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the total strain that occurs under the first roughing pressure is: Adiabatic heating during the first blanking pressure may not occur because it may not be sufficient to heat the workpiece significantly adiabatically. The first roughing reduction spacer height is greater than the main reduction spacer height.

The workpiece is press forged in the direction of the third orthogonal C-axis of the workpiece under the second rough stamping pressure to the second rough stamping spacer height at the workpiece forging temperature within the workpiece forging temperature range. .. The second blanking reduction is applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the second roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the total strain that occurs under the second roughing pressure is: Adiabatic heating during the second blanking pressure may not occur because it may not be sufficient to heat the workpiece significantly adiabatically. The height of the second roughing reduction spacer is larger than the height of the main reduction spacer.

The work piece undergoes a major reduction at a work piece forging temperature within the work piece forging temperature range in the direction of the second orthogonal B-axis of the work piece at a strain rate sufficient to adiabatically heat the interior region of the work piece. Press forged to the spacer height.

The workpiece is press-forged in the direction of the third orthogonal C-axis of the workpiece under the first roughing pressure to the first roughing reduction spacer height at the workpiece forging temperature within the workpiece forging temperature range. .. The first blanking reduction is applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the first roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the total strain that occurs under the first roughing pressure is: Adiabatic heating during the first blanking pressure may not occur because it may not be sufficient to heat the workpiece significantly adiabatically. The first roughing reduction spacer height is greater than the main reduction spacer height.

The workpiece is press forged in the direction of the first orthogonal A-axis of the workpiece under the second rough stamping pressure to the second rough stamping spacer height at the workpiece forging temperature within the workpiece forging temperature range. .. The second blanking reduction is applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the second roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the total strain that occurs under the second roughing pressure is: Adiabatic heating during the second blanking pressure may not occur because it may not be sufficient to heat the workpiece significantly adiabatically. The height of the second roughing reduction spacer is larger than the height of the main reduction spacer.

The work piece has a strain rate sufficient to adiabatically heat the interior region of the work piece, in the direction of the third orthogonal C-axis of the work piece under major pressure, within the work piece forging temperature range, and at the work piece forging temperature. It is press forged to the height of the main reduction spacer.

The workpiece is press-forged in the direction of the first orthogonal A-axis of the workpiece under the first rough stamping pressure to the first rough stamping spacer height at the workpiece forging temperature within the workpiece forging temperature range. .. The first blanking reduction is applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the first roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the total strain that occurs under the first roughing pressure is: Adiabatic heating during the first blanking pressure may not occur because it may not be sufficient to heat the workpiece significantly adiabatically. The first roughing reduction spacer height is greater than the main reduction spacer height.

The workpiece is press-forged in the direction of the second orthogonal B-axis of the workpiece under the second rough stamping pressure to a second rough stamping spacer height at a workpiece forging temperature within the workpiece forging temperature range. .. The second blanking reduction is applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the second roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the total strain that occurs under the second roughing pressure is: Adiabatic heating during the second blanking pressure may not occur because it may not be sufficient to heat the workpiece significantly adiabatically. The height of the second roughing reduction spacer is larger than the height of the main reduction spacer.

Optionally, the intermediate continuous press forging step of an embodiment of the foregoing method, the adiabatically heated interior region of the workpiece is cooled to a temperature around the workpiece forging temperature within the workpiece forging temperature range, and The outer surface region is heated up to around the workpiece forging temperature within the workpiece forging temperature. At least one of the aforementioned press forging steps of the method embodiments is repeated until a total strain of at least 1.0 is achieved in at least one region of the workpiece. In a non-limiting embodiment of the method, at least one of the press forging steps is repeated until a total strain of at least 1.0 and less than 3.5 is achieved in at least one region of the workpiece. .. In a non-limiting embodiment, the strain rate used during press forging is in the range of 0.2 sec ^{-1 to} 0.8 sec ^-1 .

The features and advantages of the devices and methods described herein may be better understood with reference to the accompanying drawings.

Plot the calculated predictions of the volume fraction of equilibrium α phase present in Ti-6-4, Ti-6-2-4-6, and Ti-6-2-4-2 alloys as a function of temperature. It is a graph to do. 3 is a flow chart listing steps of a non-limiting embodiment of a method for treating a titanium alloy according to the present disclosure. FIG. 3 is a schematic view of aspects of a non-limiting embodiment of a high strain rate multi-axis forging method using thermal management to treat a titanium alloy for grain size refinement, FIGS. c) and 3(e) represent non-limiting press forging steps, and FIGS. 3(b), 3(d), and 3(f) show optional non-limiting non-limiting aspects of the present disclosure. Represents a limited cooling and heating step. 1 is a schematic diagram of an embodiment of a prior art low strain rate multi-axis forging technique known to be used for refining the grain size of small scale samples. 3 is a flow chart listing steps of non-limiting embodiments of a method for treating a titanium alloy according to the present disclosure, including major orthogonal reductions to a final desired dimension of a workpiece and first and second roughing reductions. .. Same as above Same as above FIG. 6 is a temperature-time thermomechanical process diagram for a non-limiting embodiment of a high strain rate multi-axis forging method according to the present disclosure. FIG. 6 is a temperature-time thermomechanical process diagram for a non-limiting embodiment of a multi-temperature high strain rate multi-axis forging method according to the present disclosure. FIG. 6 is a temperature-time thermomechanical process diagram for a non-limiting embodiment of a β transus high strain rate multi-axis forging method according to the present disclosure. FIG. 6 is a schematic illustration of aspects of non-limiting embodiments of multiple upsetting and drawing methods for particle size refinement in accordance with the present disclosure. 5 is a flow chart listing steps of a non-limiting embodiment of a method for multiple upsetting and drawing processes of a titanium alloy for grain size refining according to the present disclosure. 3 is a micrograph of the microstructure of a commercially forged and treated Ti-6-2-4-2 alloy. 3 is a photomicrograph of the microstructure of a Ti-6-2-4-2 alloy processed by the thermally managed high strain MAF embodiment described in Example 1 of the present disclosure. 3 is a photomicrograph depicting the microstructure of a commercially forged and treated Ti-6-2-4-6 alloy. 3 is a photomicrograph of the microstructure of a Ti-6-2-4-6 alloy processed by the thermally controlled high strain MAF embodiment described in Example 2 of the present disclosure. 5 is a micrograph of the microstructure of a Ti-6-2-4-6 alloy processed by the thermally controlled high strain MAF embodiment described in Example 3 of the present disclosure. In a micrograph of the microstructure of a Ti-6-2-4-2 alloy processed by a thermally managed high strain MAF embodiment applying equal strain on each axis as described in Example 4 of the present disclosure. is there. Ti-6 processed using a thermally controlled high strain MAF embodiment that uses roughing reduction to minimize workpiece expansion that occurs after each major reduction, as described in Example 5 of the present disclosure. 2 is a micrograph of the microstructure of a 2-4-2 alloy. In a photomicrograph of the central region microstructure of a Ti-6-2-4-2 alloy processed by a thermally controlled high strain MAF embodiment utilizing through β transus MAF described in Example 6 of the present disclosure. is there. In a micrograph of the microstructure of the surface region of a Ti-6-2-4-2 alloy processed by a thermally controlled high strain MAF embodiment utilizing through β transus MAF described in Example 6 of the present disclosure. is there.

The reader will understand the foregoing details as well as others by considering the following detailed description of specific non-limiting embodiments according to the present disclosure.

In the present description of non-limiting embodiments, except for operational examples or otherwise indicated, all numbers expressing quantities or properties are understood as being modified by the term "about" in all examples. Should be. Accordingly, unless otherwise indicated to the contrary, any numerical parameter set forth in the following description is an approximation that may vary depending on the desired property desired to be obtained by the method according to the present disclosure. .. At a minimum, and not as an attempt to limit the application of the principles that are equivalent to the claims, each numerical parameter is at least considered by the number of significant digits reported by applying conventional rounding techniques. Should be interpreted.

Also, any numerical range recited herein is intended to include all subranges subsumed therein. For example, the range "1 to 10" has a minimum value between 1 and the maximum value 10 described (and including them), that is, a minimum value of 1 or more and a maximum value of 10 or less. , Intended to include all subranges. Any maximum numerical limitation given herein is intended to include all smaller numerical limitations contained therein, and any minimum numerical limitation given herein is contained therein. It is intended to include all higher numerical limits included. Accordingly, Applicants reserve the right to modify this disclosure, including the claims, to explicitly set out any sub-range that falls within the range explicitly stated herein. .. All such ranges are essential to the specification such that any amendment that explicitly states any such subrange is subject to the requirements of 35 USC 112, paragraph 1 and 35 USC 132(a). Are intended to be disclosed.

As used herein, the grammatical articles "one", "a", "an", and "the" include "at least one" or "one or more", unless otherwise indicated. Intended to. Thus, article is used herein to refer to the grammatical object of one or more than one (ie, at least one) article. By way of example, "component" means one or more components, and thus more than one component may be contemplated and may be or may be used in the implementation of the described embodiments. Good.

This disclosure includes a description of various embodiments. It should be understood that all embodiments described herein are exemplary, illustrative, and non-limiting. Therefore, the present invention is not limited by the description of various exemplary, illustrative, and non-limiting embodiments. Rather, the invention is capable of being modified to describe any feature explicitly or essentially described herein, or otherwise explicitly or essentially supported by this disclosure. Defined only by the range of.

Any patents, publications, or other disclosed materials referred to herein by reference in their entirety or in part are not incorporated by reference into the existing definitions, statements, or other disclosure It is incorporated herein only to the extent it does not conflict with the disclosed material. Accordingly, and to the extent necessary, the disclosure set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, which is referred to as incorporated herein by reference, but which conflicts with existing definitions, statements, or other disclosed material set forth in this disclosure, is hereby incorporated by reference. It is included only to the extent that there is no conflict with the material.

Aspects of the present disclosure relate to non-limiting embodiments of multi-axis forging processes for titanium alloys, including application of high strain rates during a grain size refining forging step. Embodiments of these methods are generally referred to in this disclosure as "high strain rate multiaxial forging" or "high strain rate MAF." As used herein, the terms "reduction" and "hit" interchangeably refer to individual press forging steps in which a workpiece is forged between die surfaces. As used herein, the phrase "spacer height" refers to the dimension or thickness of a workpiece measured along one orthogonal axis after reduction along that axis. For example, after press forging down to a spacer height of 4.0 inches along a particular axis, the thickness of the press forged workpiece measured along that axis will be about 4.0 inches. The concept and use of spacer height is well known to those skilled in the field of press forging and need not be discussed further herein.

For alloys such as the Ti-6Al-4V alloy (ASTM grade 5; UNS R56400), which may also be referred to as "Ti-6-4" alloy, a high strain rate for forging the workpiece to a total strain of at least 3.5. It has previously been determined that multiaxial forging can be used to prepare ultrafine grain billets. This process is described in US Patent Publication No. U.S. Pat. No. 12/882,538. Applying a strain of at least 3.5 can require significant processing time and complexity, adding cost and increasing the chance of unexpected problems. The present disclosure discloses a high strain rate multiaxial forging process that can provide an ultrafine grain structure using a total strain in the range of at least 1.0 up to less than 3.5.

The method according to the present disclosure is directed to titanium alloys that exhibit slower effective alpha precipitation and growth rates than Ti-6-4 alloys, such as multi-axis forging such as the multiple upset and draw (MUD) process disclosed in the '538 application. And the application of its derivatives. Specifically, Ti-6Al-2Sn-4Zr-2Mo-0.08Si alloy (UNS R54620), which is sometimes referred to as "Ti-6-2-4-2" alloy, is an additional grain such as Si. As a result of the pinning element, it has a slower effective alpha velocity than the Ti-6-4 alloy. The Ti-6Al-2Sn-4Zr-6Mo alloy (UNS R56260), which is also sometimes referred to as the "Ti-6-2-4-6" alloy, has T- as a result of increased β-stabilization content. It has a slower alpha velocity than the 6-4 alloy. From an alloying element perspective, it is recognized that α phase growth and precipitation is a function of the diffusion rate of alloying elements in titanium-based alloys. Molybdenum is known to have one of the lower diffusion rates of all titanium alloying additives. In addition, β-stabilizers such as molybdenum lower the alloy's transus temperature (T _β ), with lower T _β generally resulting in lower diffusion of atoms in the alloy at the alloy's processing temperature. As a result of the relatively slow effective alpha precipitation and growth rates of Ti-6-2-4-2 and Ti-6-2-4-6 alloys, the beta heat treatment used prior to MAF according to embodiments of the present disclosure is , Ti-6-4 alloys produce a fine and stable alpha lath size as compared to the effect of such treatments. In addition, after β heat treatment and cooling, Ti-6-2-4-2 and Ti-6-2-4-6 alloys have a fine β grain structure that limits the reaction rate of α grain growth.

The effective kinetics of α-growth can be assessed by identifying the slowest diffusing species at temperatures just below the β transus. This approach has been theoretically outlined and experimentally validated in the literature (Semiatin et al., Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science 38 (4), 10-2007, p. reference). For titanium and titanium alloys, diffusivity data for all possible alloying elements are not readily available, however, literature studies such as those by Lutjering and Williams in Titanium (2nd edition, 2007) are not available. , Generally agree with the following relative rankings for some common alloying elements:
_{D Mo <D Nb <D Al} ~D V ~D Sn ~D Zr ~D Hf <D Cr ~D Ni ~D Cr ~D Co ~D Mn ~D Fe

Therefore, alloys containing molybdenum, such as Ti-6-2-4-6 alloy and Ti-6-2-4-2 alloy, are better than Ti-6-4 alloy whose reaction rate is controlled by diffusion of aluminum. Also exhibits the desired low α-velocity required to achieve ultrafine grained microstructure at relatively slow strains. Based on the family relationships of the Periodic Table, tantalum and tungsten can be reasonably assumed to belong to the family of slow diffusers.

Reducing the β transus temperature in alloys controlled by aluminum diffusion, in addition to the inclusion of slow diffusing elements to reduce the effective reaction rate of the α phase, would have a similar effect. A β transus temperature reduction of 100° C. will generally reduce the diffusivity of aluminum in the β phase by order of magnitude at the β transus temperature. The α-velocity of alloys such as ATI 425® alloy (Ti-4Al-2.5V; UNS 54250) and Ti-6-6-2 alloy (Ti-6Al-6V-2SN; UNS 56620) depends on aluminum diffusion. However, the lower β-transus temperature of these alloys as compared to the Ti-6Al-4V alloy also results in the desired slower effective α-reaction rate. The Ti-6Al-7Nb alloy (UNS R56700), which is usually a biomedical version of the Ti-6Al-4V alloy, can also exhibit a slower effective alpha rate due to the niobium content.

It was initially expected that α+β alloys other than Ti-6-4 alloys could be processed under conditions similar to those disclosed in the '538 application at temperatures that result in similar α volume fractions. For example, Ti-6-4 alloy at 1500°F (815.6°C) was predicted to be 1600 using a commercial computer tool, PANDAT software, available from Computherm, LLC, Madison, Wisconsin, USA. Almost the same α phase as both the Ti-6-2-4-2 alloy at °F (871.1°C) and the Ti-6-2-4-6 alloy at 1200°F (648.9°C). It was expected to have a volume fraction (see Figure 1). However, both Ti-6-2-4-2 and Ti-6-2-4-6 alloys were submitted to the '538 application using temperatures that would be expected to produce similar alpha phase volume fractions. When the Ti-6-4 alloy was treated in the same manner, severe cracking occurred. Lower α-equilibrium volume fractions and/or much higher temperatures resulting in significantly reduced strain per pass have been successful for Ti-6-2-4-2 and Ti-6-2-4-6 alloys. Was needed to process.

Each transformation to a high strain rate MAF process, including α/β forging temperature(s), strain rate, strain per hit, hold time between hits, number and interval of reheats, and intermediate heat treatments , Can affect the resulting microstructure and the presence and extent of cracks. Lower total strains were initially attempted to inhibit cracking without the expectation that an ultrafine grained structure would occur. However, upon investigation, the samples processed using the lower total strain showed significant promise for producing ultrafine grained structures. This result was totally unexpected.

In a non-limiting embodiment according to the present disclosure, a method for producing ultrafine grain size includes the following steps: 1) a titanium alloy that exhibits a lower effective alpha phase growth rate than Ti-6-4 alloy. 2) β-annealing the titanium alloy to produce a fine and stable α lath size, and 3) at least 1.0, or in another embodiment, at least 1.0 up to 3. High strain rate MAF up to a total strain of less than 5 (or a similar derivative process such as the multiple upset and stretch (MUD) process disclosed in the '538 application). As used herein, the term “fine” to describe grain and lath size refers to the smallest grain and lath size that can be achieved, and in a non-limiting embodiment, about 1 μm. The term "stable" is used herein to mean that the multi-axis forging step does not significantly coarsen the α-grain size and does not increase the α-grain size by more than about 100%. ..

The flow chart of FIG. 2 and the schematic diagram of FIG. 3 are aspects of a non-limiting embodiment of the present disclosure of a method (16) for refining titanium alloy grain size using high strain rate multiaxial forging (MAF). Exemplify Prior to multi-axis forging (26), the titanium alloy workpiece 24 is beta annealed (18) and cooled (20). Air cooling is possible on smaller workpieces, such as 4 inch cubes, however, water or liquid cooling can also be used. Faster cooling rates result in finer lath sizes and alpha particle sizes. The β-annealing (18) comprises heating the workpiece 24 above the β-transus temperature of the titanium alloy of the workpiece 24 and holding it for a time sufficient to form all β-phases in the workpiece 24. including. Beta anneal (18) is a process well known to those of ordinary skill in the art and is therefore not described in detail herein. A non-limiting embodiment of β-annealing involves heating the workpiece 24 to a β-annealing temperature that is about 50° F. (27.8° C.) above the β-transus temperature of the titanium alloy, and at that temperature. Holding for about 1 hour.

After the β anneal (18), the workpiece 24 is cooled (20) to a temperature below the β transus temperature of the titanium alloy of the workpiece 24. In a non-limiting embodiment of the present disclosure, the workpiece is cooled to ambient temperature. As used herein, "ambient temperature" refers to ambient temperature. For example, in a non-limiting commercial production scenario, "ambient temperature" refers to the temperature around the factory. In a non-limiting embodiment, cooling (20) can include quenching. Quenching is a process understood by those skilled in the metallurgical arts, including immersing the workpiece 24 in water, oil, or another suitable liquid. In other non-limiting embodiments, cooling (20) can include air cooling, particularly for smaller size workpieces. Any method of cooling titanium alloy workpiece 24 now or in the future known to those skilled in the art is within the scope of the present disclosure. Additionally, in certain non-limiting embodiments, cooling (20) includes direct cooling to a workpiece forging temperature within a workpiece forging temperature range for subsequent high strain rate multi-axis forging. ..

After cooling the workpiece (20), the workpiece is subjected to high strain rate multi-axis forging (26). As will be appreciated by those skilled in the art, multiaxial forging ("MAF"), sometimes referred to as "ABC" forging, is a form of severe plastic deformation. High strain rate multi-axis forging (26), in accordance with a non-limiting embodiment of the present disclosure, includes a workpiece 24 containing a titanium alloy, a workpiece within a workpiece forging temperature range within the α+β phase region of the titanium alloy. After heating to the forging temperature (step 22 in Figure 2), the MAF (26) using high strain rate is included. Obviously, in embodiments where the cooling step (20) includes cooling to a temperature within the workpiece forging temperature range, the heating step (22) is not required.

The high strain rate is used in the high strain rate MAF to adiabatically heat the interior region of the workpiece. However, in a non-limiting embodiment according to the present disclosure, the temperature of the internal region of the titanium alloy workpiece 24 is at least the final cycle of the high strain rate MAF ABC hit during the cycle when the temperature of the titanium alloy workpiece is The β transus temperature (T _β ) should not be exceeded. Thus, in such a non-limiting embodiment, the workpiece forging temperature for at least the final cycle of the ABC hit, or at least the last hit of the cycle of the high strain rate MAF, during the high strain rate MAF is: It should be selected to ensure that the temperature in the internal region of the workpiece does not equal or exceed the beta transus temperature of the alloy. For example, in a non-limiting embodiment according to the present disclosure, the temperature of the interior region of the workpiece has a total strain of at least 1.0, or at least 1.0 and at least 1.0 up to less than 3.5. When achieved in one region, the beta transus temperature of the alloy is 20° F. (11.1) during at least the final high strain rate cycle of the ABC hit in MAF, or at least during the final press forging hit. ° C.) below the temperature, i.e., does not exceed _{T β -20 ° F (T β} -11.1 ℃).

In a non-limiting embodiment of high strain rate MAF according to the present disclosure, the workpiece forging temperature includes a temperature within the workpiece forging temperature range. In a non-limiting embodiment, the workpiece forging temperature range is 100° F (55.6° C.) below the β-transus temperature (T _β ) of the titanium alloy of the workpiece to 700° β-transus temperature of the titanium alloy. The temperature is below F (388.9° C.). In yet another non-limiting embodiment, the workpiece forging temperature range is 300°F (166.7°C) below the β transus temperature of the titanium alloy to 625°F (347°C) of the β transus temperature of the titanium alloy. ) Below the temperature. In a non-limiting embodiment, the lower end of the workpiece forging temperature range is the temperature within the α+β phase region where damage, such as crack formation and gouging, does not occur on the surface of the workpiece during a forging hit.

In the non-limiting method embodiment shown in FIG. 2 applied to a Ti-6-2-4-2 alloy having a β transus temperature (T _β ) of about 1820° F. (996° C.), the workpiece forging is The temperature range may be from 1120°F (604.4°C) to 1720°F (937.8°C), or in another embodiment, from 1195°F (646.1°C) to 1520°F( 826.
7° C.). In the non-limiting method embodiment shown in FIG. 2 applied to a Ti-6-2-4-6 alloy having a β transus temperature (T _β ) of about 1720° F. (940° C.), workpiece forging is performed. The temperature range may be 1020°F (548.9°C) to 1620°F (882.2°C), or in another embodiment, 1095°F (590.6°C) to 1420°F( 771.1°C). In another non-limiting embodiment, the embodiment shown in FIG. 2 is sometimes referred to as a "Ti-4Al-2.5V" alloy and has a β of about 1780°F (971.1°C). When applied to ATI 425® alloy (UNS R54250) having a transus temperature (T _β ), the workpiece forging temperature range is from 1080°F (582.2°C) to 1680°F (915.6°C). Or in another embodiment, from 1155°F (623.9°C) to 1480°F (804.4°C). In yet another non-limiting embodiment, the embodiment of the present disclosure of FIG. 2 is sometimes referred to as a “Ti-6-6-2” alloy and has a temperature of about 1735° F. (946.1° C.). When applied to a Ti-6Al-6V-2Sn alloy (UNS 56620) having a β transus temperature (T _β ), the workpiece forging temperature range is from 1035°F (527.2°C) to 1635°F (890.6). C.), or in another embodiment, between 1115° F. (601.7° C.) and 1435° F. (779.4° C.). The present disclosure is directed to high strain rate multiaxial forging and its derivatives, such as titanium alloys having lower effective alpha precipitation and growth rates than Ti-6-4 alloy, such as the MUD method disclosed in the '538 application. Including the application of.

Referring again to FIGS. 2 and 3, when the titanium alloy workpiece 24 is at the workpiece forging temperature, the workpiece 24 is subjected to a high strain rate MAF (26). In a non-limiting embodiment according to the present disclosure, the MAF (26) heats the workpiece adiabatically, or at least heats an interior region of the workpiece adiabatically to plastically deform the workpiece 24. Press forging the workpiece 24 at a workpiece forging temperature in the direction (A) of the first orthogonal axis 30 of the workpiece using a sufficient strain rate (step 28 shown in FIG. 3(a)). )including.

High strain rates and high ram rates are used to adiabatically heat the interior region of the workpiece in a non-limiting embodiment of high strain rate MAF according to the present disclosure. In a non-limiting embodiment according to the present disclosure, the term "high strain rate" refers to a strain rate in the range of about 0.2 sec " ¹ to about 0.8 sec " ¹ . In another non-limiting embodiment according to the present disclosure, the term "high strain rate" refers to a strain rate within the range of about 0.2 sec " ¹ to about 0.4 sec " ¹ .

In a non-limiting embodiment according to the present disclosure using the high strain rate defined above, the internal region of the titanium alloy workpiece is thermally insulated to a temperature above the workpiece forging temperature of about 200°F (111.1°C). May be heated. In another non-limiting embodiment, during press forging, the interior region is within a temperature range of about 100° F. (55.6° C.) to about 300° F. (166.7° C.) above the workpiece forging temperature. Heated adiabatically to temperature. In yet another non-limiting embodiment, during press forging, the internal region is within a temperature range of about 150°F (83.3°C) to about 250°F (138.9°C) above the workpiece forging temperature. Is heated adiabatically to the temperature of. As noted above, in a non-limiting embodiment, any portion of the work piece is made of titanium alloy during the last cycle of the high strain rate AB-CMAF hit or during the last hit on the orthogonal axis. It should not be heated above the β transus temperature.

In a non-limiting embodiment, during press forging (28), the workpiece 24 is plastically deformed to a height within a range of 20% to 50% or a reduction in another dimension, i.e., a dimension within this range. It is reduced to the ratio of. In another non-limiting embodiment, during press forging (28), the workpiece 24 is plastically deformed to a height in the range of 30%-40% or a reduction at another dimension.

The known ultra low strain rate (0.001 sec ^-1 or less) multiaxial forging process is schematically depicted in FIG. In general, aspects of multi-axis forging are such that after every 3 strokes (ie, "3 hits") by a forging device (which may be, for example, free forging), the shape and size of the workpiece is determined by its 3 hit cycle. Is approaching the shape and size of the workpiece just before the first hit of. For example, a cube-shaped workpiece 5 inches on a side is first forged with a first "hit" in the direction of the "a" axis, rotated 90°, and a second hit in the direction of the orthogonal "b" axis. After forging, then rotating 90°, and forging with a third hit in the direction of the orthogonal “c” axis, the workpiece will resemble the starting cube and will contain approximately 5 inches of sides. In other words, the three-hit cycle caused the cube to deform in three steps along the three orthogonal axes of the cube, but with the result of repositioning the workpiece between individual hits and the reduction selection during each hit. The overall result of the three forging deformations is to return the cube to approximately its original shape and size.

In another non-limiting embodiment according to the present disclosure, a first press forging step (28), shown in FIG. 2( a) and also referred to herein as “first hit”, is performed when the workpiece is It may include press forging the workpiece, face down, to a predetermined spacer height while at a temperature within the workpiece forging temperature range. As used herein, the term "spacer height" refers to the dimensions of the workpiece at the completion of a particular press forging press. For example, for a spacer height of 5 inches, the workpiece is forged to a size of about 5 inches. In certain non-limiting embodiments of the disclosed method, the spacer height is, for example, 5 inches. In another non-limiting embodiment, the spacer height is 3.25 inches. Other spacer heights, such as less than 5 inches, about 4 inches, about 3 inches, more than 5 inches, or 5 inches up to 30 inches are within the scope of the embodiments herein, but within the scope of the present disclosure. Should not be seen as limiting. The spacer height is the capacity of the forging furnace, and optionally the capacity of the thermal management system according to the non-limiting embodiments of the present disclosure to maintain the workpiece at the workpiece forging temperature, as found herein. Limited only by. Spacer heights of less than 3 inches are also within the scope of the embodiments disclosed herein, and such relatively small spacer heights are limited only by the desired properties of the final product. For example, the use of spacer heights of about 30 inches in a method according to the present disclosure may result in billet-sized (eg, 30 inches on a side) cubic shaped titanium having fine, fine, or ultrafine grain sizes. Allows the production of alloy forms. The conventional alloy billet-sized cube-shaped morphology is used, for example, as workpieces that are forged into disks, rings, and case parts for aircraft or land turbines.

The predetermined spacer height to be used in various non-limiting embodiments of the methods according to the present disclosure can be determined by one of ordinary skill in the art in view of the present disclosure without undue experimentation. The particular spacer height can be determined by one of ordinary skill in the art without undue experimentation. The particular spacer height depends on the susceptibility of the particular alloy to cracking during forging. Alloys with higher susceptibility to cracking will require larger spacer heights, ie less deformation per hit to prevent cracking. Limitation of adiabatic heating also workpiece temperature, because should not exceed T _beta alloys in at least the last cycle of hits, must be considered in selecting a spacer height. In addition, the limitation of forging press capability needs to be taken into account when choosing the spacer height. For example, during the pressing of a 4-inch cube work piece, the cross-sectional area increases during the pressing step. Therefore, the total load required to continue deforming the workpiece at the required strain rate increases. The load cannot increase beyond the capacity of the forging press. Also, the workpiece geometry needs to be considered when selecting the spacer height. Large deformation can result in expansion of the workpiece. An excessively large reduction can result in relative flattening of the workpiece, so that subsequent forging hits in different orthogonal axis directions can result in bending of the workpiece.

In certain non-limiting embodiments, the spacer height used for each orthogonal axis hit is equal. In certain other non-limiting embodiments, the spacer heights used for each orthogonal axis hit are not equal. Non-limiting embodiments of high strain rate MAF using non-equal spacer heights on each orthogonal axis are presented below.

After press forging (28) the workpiece 24 in the direction of the first orthogonal axis 30, ie, the A direction shown in FIG. 3( a ), a non-limiting embodiment of the method according to the present disclosure is optional. Further comprising cooling the temperature of an adiabatically heated interior region (not shown) of the workpiece to a temperature at or near the workpiece forging temperature within the workpiece forging temperature range (step 32), Is shown in FIG. In various non-limiting embodiments, the internal zone cooling time, or “wait” time, may range, for example, from 5 seconds to 120 seconds, 10 seconds to 60 seconds, or 5 seconds to 5 minutes. In various non-limiting embodiments according to the present disclosure, as used herein, the "adiabatically heated interior region" of a workpiece extends outwardly from the center of the workpiece, Refers to a region having a volume of at least about 50%, or at least about 60%, or at least about 70%, or at least about 80%. The time required to cool the interior region of the workpiece to a temperature at or near the workpiece forging temperature depends on the size, shape, and composition of the workpiece 24 and the atmospheric conditions surrounding the workpiece 24. It will be appreciated by those skilled in the art that it will depend.

During the internal zone cooling period, aspects of the thermal management system 33 according to certain non-limiting embodiments disclosed herein optionally cause the outer surface area 36 of the workpiece 24 to be at or below the workpiece forging temperature. Including heating to a near temperature (step 34). In this way, the temperature of the workpiece 24 is at or near uniform and is at or near a substantially isothermal condition to the workpiece forging temperature before each high strain rate MAF hit. .. Optionally, heating (34) the outer surface region 36 of the workpiece 24 after each A-axis heat, after each B-axis hit, and/or after each C-axis hit may be within the scope of the present disclosure. Be recognized. In a non-limiting embodiment, the outer surface of the workpiece is optionally heated (34) after each cycle of an ABC hit. In yet another non-limiting embodiment, the outer surface area is optionally heated after any hit or cycle of hits as long as the overall temperature of the workpiece is maintained within the workpiece forging temperature range during the forging process. To be done. Prior to each high strain rate MAF hit, the time to heat the workpiece to maintain the temperature of the workpiece 24 at or near uniform and substantially isothermal to or near the workpiece forging temperature is: , May depend on the size of the workpiece, and this can be determined by one of ordinary skill in the art without undue experimentation. In various non-limiting embodiments according to the present disclosure, as used herein, the "outer surface area" of a workpiece extends inwardly from the outer surface of the workpiece and comprises at least about 50% of the workpiece. , Or at least about 60%, or at least about 70%, or at least about 80% volume. This is recognized at any time in between.

In a non-limiting embodiment, heating (34) the outer surface area 36 of the workpiece 24 may be accomplished using one or more surface heating mechanisms 38 of the thermal management system 33. As an example of a continuous press forging step of a possible surface heating mechanism, the entire workpiece can be placed in a furnace or otherwise heated to temperatures associated with the workpiece forging temperature range.

In certain non-limiting embodiments, as an optional feature, during each of the A, B, and C forging hits, the thermal management system 33 is used to heat the outer surface area 36 of the workpiece. The adiabatically heated inner region is cooled during the inner region cooling time, and the temperature of the workpiece returns to a substantially uniform temperature or a temperature close to the workpiece forging temperature of choice. In certain other non-limiting embodiments according to this disclosure, as an optional feature, during each of the A, B, and C forging hits, thermal management system 33 heats outer surface area 36 of the workpiece. The adiabatically heated interior region used to cool the interior region is cooled during the interior region cooling time so that the temperature of the workpiece returns to a substantially uniform temperature within the workpiece forging temperature range. As used herein, (1) a thermal management system 33 for heating the outer surface area of the workpiece to a temperature within the workpiece forging temperature range, and (2) an adiabatically heated inner area, Non-limiting embodiments according to the present disclosure that utilize both the time between cooling to temperatures within the forging temperature range are sometimes referred to as "heat controlled high strain rate multiaxial forging." 38 includes, but is not limited to, a flame heater adapted for flame heating of the outer surface of the workpiece 24, an induction heater adapted for induction heating, and a radiant heater adapted for radiant heating. Other mechanisms and techniques for heating the outer surface region of the workpiece will be apparent to those of ordinary skill in the art in view of this disclosure, and such features and techniques are within the scope of the disclosure. A non-limiting embodiment of the outer surface area heating mechanism 38 may include a box furnace (not shown). A box furnace uses an outer surface of a workpiece that employs one or more of a flame heating mechanism, a radiant heating mechanism, an induction heating mechanism, and any other suitable heating mechanism now or in the future known to those skilled in the art. It may be configured with various heating mechanisms for heating the area.

In another non-limiting embodiment, the temperature of the outer surface region 36 of the work piece 24 is optionally heated (34) using one or more die heaters 40 of the thermal management system 33 and the work piece Maintained within the workpiece forging temperature range at or near the piece forging temperature. The die heater 40 can be used to maintain the die 42 or the die press forging surface 44 of the die at or near the workpiece forging temperature, or within the workpiece forging temperature range. In a non-limiting embodiment, the thermal management system die 42 is heated to a temperature within a range that includes a workpiece forging temperature to a temperature below the workpiece forging temperature of 100°F (55.6°C). The die heater 40 is any suitable heating mechanism known to those skilled in the art now or in the future, including, but not limited to, a flame heating mechanism, a radiant heating mechanism, a conduction heating mechanism, and/or an induction heating mechanism. May heat the die 42 or die press forged surface 44. In a non-limiting embodiment, the die heater 40 may be a component of a box furnace (not shown). The thermal management system 33 is shown to be placed and used during the cooling steps (32), (52), (60) of the multi-axis forging process (26) (FIG. 3(b), ( d), and (f)), the thermal management system 33 during the press forging steps (28), (46), (56) as depicted in FIGS. 3(a), (c), and (e). It will be appreciated that it may or may not be located at.

As shown in FIG. 3( c ), aspects of a non-limiting embodiment of a multi-axis forging method (26) according to the present disclosure include adiabatically heating the workpiece 24 or at least an interior region of the workpiece 24, Forging the workpiece 24 in the direction (B) of the second orthogonal axis 48 of the workpiece 24 using a strain rate sufficient to plastically deform the workpiece 24 within the workpiece forging temperature range. Press forging at temperature (step 46). In a non-limiting embodiment, during press forging (46), the workpiece 24 is deformed to a plastic deformation of 20% to 50% under height or another dimension. In another non-limiting embodiment, during press forging (46), workpiece 24 is deformed to a plastic deformation of 30% to 40% under height or another dimension. In a non-limiting embodiment, the workpiece 24 may be press forged in the direction of the second orthogonal axis 48 to the same spacer height as used in the first press forging step (28) ( 46). In another non-limiting embodiment, the workpiece 24 may be press forged in the direction of the second orthogonal axis 48 to a spacer height different from that used in the first press forging step (28). Good. In another non-limiting embodiment, the inner region (not shown) of the workpiece 24 is adiabatically heated during the press forging step (46) to the same temperature as the first press forging step (28). In another non-limiting embodiment, the high strain rate used for press forging (46) is within the same strain rate range as disclosed for the first press forging step (28).

In a non-limiting embodiment, as shown in FIGS. 3( b) and (d ), the workpiece 24 has successive press-forging steps (eg, such that it presents different orthogonal axes to the forging surface). It can be rotated (50) during (28), (46), (56). This rotation is sometimes referred to as an "ABC" rotation. By using different forging furnace configurations, it may be possible to rotate the ram on the forging furnace instead of rotating the workpiece 24, or the forging furnace may rotate either the workpiece or the forging furnace. It will be appreciated that a multi-axis ram may be equipped as it is not required. Obviously, an important aspect is the relative change in the position of the workpiece and ram used, and rotation of the workpiece 24 (50) may be unnecessary or optional. .. However, in modern industrial equipment settings, rotating the workpiece (50) about different orthogonal axes during the press forging step would be required to complete the multi-axis forging process (26). Let's do it.

In a non-limiting embodiment where an A-B-C rotation (50) is required, the workpiece 24 is either manually by a forging furnace operator to provide the A-B-C rotation (50), Or it can be rotated by an automatic rotation system (not shown). As an automatic ABC rotation system, such as to allow free swing clamp operator tools, or non-limiting thermally controlled high strain rate multi-axis forging embodiments disclosed herein. It may include, but is not limited to, the like.

After press forging (46) the workpiece 24 in the direction of the second orthogonal axis 48, ie, the B direction, as shown in FIG. 3(d), the process (20) optionally includes insulating the workpiece. The method further includes allowing the heated inner region (not shown) to cool to a temperature at or near the workpiece forging temperature (step 52), which is shown in Figure 3(d). In certain non-limiting embodiments, the internal zone cooling time or waiting time may range, for example, from 5 seconds to 120 seconds, or 10 seconds to 60 seconds, or 5 seconds to up to 5 minutes. It will be appreciated by those skilled in the art that the minimum cooling time depends on the size, shape, and composition of the workpiece 24 and the characteristics of the environment around the workpiece.

During an optional internal zone cooling period, an optional aspect of the thermal management system 33 according to certain non-limiting embodiments disclosed herein allows the outer surface area 36 of the workpiece 24 to move to a workpiece forging temperature. Or heating to a temperature within or close to the workpiece forging temperature range (step 54). In this way, the temperature of the workpiece 24 is at or near uniform and is substantially isothermal to or near the workpiece forging temperature prior to each high strain rate MAF hit. Maintained. In a non-limiting embodiment, when the adiabatically heated interior region is allowed to cool for a particular interior region cooling time and when the thermal management system 33 is used to heat the outer surface region 36, the temperature of the workpiece is reduced. Returns to or near a substantially uniform workpiece forging temperature temperature between each ABC forging hit. In another non-limiting embodiment according to the present disclosure, when the adiabatically heated interior region is allowed to cool for a particular interior region cooling time and the thermal management system 33 is used to heat the outer surface region 36. , The temperature of the workpiece returns to a substantially uniform temperature within the workpiece forging temperature range prior to each high strain rate MAF hit.

In a non-limiting embodiment, heating (54) outer surface area 36 of workpiece 24 may be accomplished using one or more outer surface heating features 38 of thermal management system 33. Examples of possible heating mechanisms 38 include a flame heater adapted for flame heating of the workpiece 24, an induction heater adapted for induction heating, and/or a radiant heater adapted for radiant heating. Yes, but not limited to. Non-limiting embodiments of the surface heating mechanism 38 may include a box furnace (not shown). Other mechanisms and techniques for heating the outer surface of the workpiece will be apparent to those of ordinary skill in the art in view of the present disclosure, and such features and techniques are within the scope of the present disclosure. The box furnace may be configured with various heating mechanisms for heating the outer surface of the workpiece, such heating mechanisms including flame heating mechanisms, radiant heating mechanisms, induction heating mechanisms, and/or current or future present heating mechanisms. One or more of any other heating mechanism known to those of skill in the art may be included.

In another non-limiting embodiment, the temperature of the outer surface region 36 of the workpiece 24 is heated (54) using one or more die heaters 40 of the thermal management system 33 to produce a workpiece forging temperature. At or near that temperature, it can be maintained within the workpiece forging temperature range. The die heater 40 can be used to maintain the die 42 or the die press forging surface 44 of the die at or near the workpiece forging temperature, or within the workpiece forging temperature range. The die heater 40 is any suitable heating mechanism known to those skilled in the art now or in the future, including, but not limited to, a flame heating mechanism, a radiant heating mechanism, a conduction heating mechanism, and/or an induction heating mechanism. May heat the die 42 or die press forged surface 44. In a non-limiting embodiment, the die heater 40 may be a component of a box furnace (not shown). The thermal management system 33 is shown to be placed and used during the balancing and cooling steps (32), (52), (60) of the multi-axis forging process (26) (see FIG. 3(b). ), (d), and (f)), the thermal management system 33 includes press forging steps (28), (46), () as depicted in FIGS. 3(a), (c), and (e). It will be appreciated that it may or may not be placed in 56).

As shown in FIG. 3(e), an aspect of an embodiment of a multi-axis forging method (26) according to the present disclosure is that the workpiece 24 is heated adiabatically, or the interior region of the workpiece is at least adiabatically. Using the ram and strain rates sufficient to heat and plastically deform the workpiece 24, the workpiece 24 is oriented in the direction of the third orthogonal axis 58 of the workpiece 24 (C) at the workpiece forging temperature. Press forging (step 56) at a workpiece forging temperature within the range. In a non-limiting embodiment, the workpiece 24 is deformed during press forging (56) to a plastic deformation of 20% to 50% under height or another dimension. In another non-limiting embodiment, during press forging (56), the workpiece is deformed to a plastic deformation of 30% to 40% under height or another dimension. In a non-limiting embodiment, the workpiece 24 has a third orthogonal axis at the same spacer height as that used in the first press forging step (28) and/or the second forging step (46). It may be press forged in the direction of 58 (56). In another non-limiting embodiment, the workpiece 24 may be press forged in the direction of the third orthogonal axis 58 to a spacer height different from that used in the first press forging step (28). Good. In another non-limiting embodiment according to the present disclosure, an inner region (not shown) of the workpiece 24 is adiabatically heated during the press forging step (56) to the same temperature as the first press forging step (28). To be done. In another non-limiting embodiment, the high strain rate used for press forging (56) is within the same strain rate range as disclosed for the first press forging step (28).

In a non-limiting embodiment, the work piece 24 is subjected to continuous press forging steps (e.g., 46, 56), as indicated by the arrow 50 in FIGS. ) Can be rotated (50) about different orthogonal axes. As mentioned above, this rotation is sometimes referred to as an ABC rotation. By using different forging furnace configurations, it may be possible to rotate the ram on the forging furnace instead of rotating the workpiece 24, or the forging furnace may rotate either the workpiece or the forging furnace. It will be appreciated that a multi-axis ram may be equipped as it is not required. Therefore, rotation 50 of workpiece 24 may be an unnecessary or optional step. However, in modern industrial settings, rotating the workpiece (50) about different orthogonal axes during the press forging step would be required to complete the multi-axis forging process (26). ..

After press forging 56 the workpiece 24 in the direction of the third orthogonal axis 58, ie, the C direction, as shown in FIG. 3(e), the process 20 optionally heats the workpiece adiabatically. The method further includes allowing an interior region (not shown) to cool to a temperature at or near the workpiece forging temperature (step 60), which is shown in Figure 3(f). The internal zone cooling time may range, for example, from 5 seconds to 120 seconds, 10 seconds to 60 seconds, or 5 seconds to up to 5 minutes, and the cooling time may vary with the size, shape, and composition of the workpiece 24. , As well as those of the environment surrounding the workpiece will be recognized by those skilled in the art.

During an optional cooling period, an optional aspect of the thermal management system 33 according to the non-limiting embodiments disclosed herein causes the outer surface area 36 of the workpiece 24 to move to or below the workpiece forging temperature. Including heating to a near temperature (step 62). In this way, the temperature of the workpiece 24 is at or near uniform and is substantially isothermal to or near the workpiece forging temperature prior to each high strain rate MAF hit. Maintained. In a non-limiting embodiment, the adiabatically heated interior region is allowed to cool for a particular interior region cooling time, and the outer surface region 36 of the workpiece is heated by using the thermal management system 33. The temperature returns to or near that of the substantially uniform workpiece forging temperature between each ABC forging hit. In another non-limiting embodiment according to the present disclosure, the adiabatically heated interior region is allowed to cool for a particular interior region cooling time and the thermal management system 33 is used to heat the outer surface region 36. Causes the temperature of the workpiece to return to a substantially isothermal condition within the workpiece forging temperature range between successive ABC forging hits.

In a non-limiting embodiment, heating (62) the outer surface region 36 of the workpiece 24 may be accomplished using one or more outer surface heating features 38 of the thermal management system 33. Examples of possible heating mechanisms 38 may include a flame heater for flame heating of the workpiece 24, a adapted induction heater for induction heating, and/or a radiant heater for radiant heating, It is not limited to these. Other mechanisms and techniques for heating the outer surface of the workpiece will be apparent to those of ordinary skill in the art in view of the present disclosure, and such features and techniques are within the scope of the present disclosure. Non-limiting embodiments of the surface heating mechanism 38 may include a box furnace (not shown). Box furnaces use a flame heating mechanism, a radiant heating mechanism, an induction heating mechanism, and/or any other suitable heating mechanism known to those of ordinary skill in the art at the present time or in the future, for a workpiece. It may be configured with various heating mechanisms for heating the outer surface.

In another non-limiting embodiment, the temperature of the outer surface region 36 of the workpiece 24 is heated (62) using one or more die heaters 40 of the thermal management system 33, the workpiece forging temperature. At or near that temperature, it can be maintained within the workpiece forging temperature range. The die heater 40 can be used to maintain the die 42 or the die press forging surface 44 of the die at or near the workpiece forging temperature, or within a temperature forging range. In a non-limiting embodiment, the thermal management system die 42 is heated to a temperature within a range that includes a workpiece forging temperature to a temperature below the workpiece forging temperature of 100°F (55.6°C). The die heater 40 is any suitable heating mechanism known to those skilled in the art now or in the future, including, but not limited to, a flame heating mechanism, a radiant heating mechanism, a conduction heating mechanism, and/or an induction heating mechanism. May heat the die 42 or die press forged surface 44. In a non-limiting embodiment, the die heater 40 may be a component of a box furnace (not shown). The thermal management system 33 is located and shown to be used during the balancing steps (32), (52), (60) of the multi-axis forging process (FIGS. 3(b), (d)). , And (f)), the thermal management system 33 may be located in the press forging steps 28, 46, 56 as depicted in FIGS. 3(a), (c), and (e), or It will be appreciated that it need not be placed.

Aspects of the present disclosure include non-limiting embodiments in which one or more of the press forging steps along the three orthogonal axes of the workpiece are repeated until a total strain of at least 1.0 is achieved in the workpiece. including. Total strain is total true strain. The phrase "true strain" is also known to those skilled in the art as "logarithmic strain" or "effective strain". Referring to FIG. 2, this is press forging until step (g), ie, a total strain of at least 1.0, or at least 1.0 and up to less than 3.5 is achieved in the workpiece. Illustrated by repeating (step 64) one or more of steps (28), (46), (56). After the desired strain has been achieved in either the press forging step (28) or (46) or (56), no further press forging is necessary and there is an optional balancing step (ie Allowing the inner region to cool to or near the workpiece forging temperature (32) or (52) or (60), and the outer surface of the workpiece (34) or (54) or (62) forging the workpiece. Temperature is not required), the workpiece is cooled to ambient temperature, in a non-limiting embodiment by quenching in a liquid, or in another non-limiting embodiment. It is further recognized that it may simply be cooled by air cooling or any faster cooling.

It will be appreciated that, as disclosed herein, in a non-limiting embodiment, the total strain is the total strain in the entire work piece after multi-axis forging. In a non-limiting embodiment according to the present disclosure, the total strain may include equal strain on each orthogonal axis, or the total strain may include different strains on one or more orthogonal axes.

According to a non-limiting embodiment, after beta annealing, the workpiece can be multi-axis forged at two different temperatures within the alpha+beta phase region. For example, referring to FIG. 3, the iterative step (64) of FIG. 2 includes steps (a)-(optional b), (c)-(optional d), and (e)-(optional). repeating one or more of f) at a first temperature in the α+β phase region until a particular strain is achieved, and then steps (a)-(optional b), (c) )-(Optional d), and (e)-(optional f) one or more of the final press forging steps (a), (b), or (c) (ie (28). , (46), (56)), a second strain in the α+β phase region until a total strain of at least 1.0, or at least 1.0 and up to less than 3.5 is achieved in the workpiece. Can be repeated at the temperature of. In a non-limiting embodiment, the second temperature in the α+β phase region is lower than the first temperature in the α+β phase region. MAF press forging temperature above one or more of steps (a)-(optional b), (c)-(optional d), and (e)-(optional f) It is recognized that carrying out the method as repeated at is within the scope of the present disclosure as long as the temperature is within the forging temperature range. It is also recognized that in a non-limiting embodiment, the second temperature in the α+β phase region is higher than the first temperature in the α+β phase region.

In a non-limiting embodiment according to the present disclosure, different reductions are used for A-axis hits, B-axis hits, and C-axis hits to provide equalized strain in all directions. Applying a high strain rate MAF to introduce equalized strain in all directions results in fewer cracks in the workpiece, and more equiaxed alpha grain structure on the workpiece. For example, non-equalized strain can be introduced into a cubic workpiece by starting with a 4-inch cube forged at a high strain rate to a height of 3.0 inches on the A-axis. This reduction on the A axis causes the workpiece to expand along the B and C axes. If the second reduction in the B-axis direction reduces the B-axis dimension to 3.0 inches, more strain is introduced into the workpiece on the B-axis than on the A-axis. Similarly, a subsequent hit in the C-axis direction that reduces the C-axis dimension to 3.0 inches will introduce more strain into the workpiece on the C-axis than on the A-axis or B-axis. .. As another example, a 4-inch cube workpiece is forged ("hit") on the A-axis to a height of 3.0 inches to introduce equalized strain in all orthogonal directions, 90 It is rotated a degree and hits 3.5 inches high on the B-axis, then 90 degrees and hits 4.0 inches high on the C-axis. This latter sequence is about 4 inches on a side, resulting in a cube with equalized strain in each orthogonal direction of the cube. A general equation for calculating the reduction on each orthogonal axis of a cubic workpiece during high strain rate MAF is provided in equation 1.
Equation 1: Strain = -ln (spacer height/starting height)
A general equation for calculating total strain is provided by equation 2:
Different reductions can be performed by using spacers in the forging equipment that provide different spacer heights, or by any alternative method known to those skilled in the art.

Referring now to FIG. 5, and considering FIG. 3, in a non-limiting embodiment according to the present disclosure, a process (70) for the production of an ultra-fine grain titanium alloy comprises beta annealing a titanium alloy workpiece. (71), cooling the β-annealed workpiece 24 to a temperature below the β transus temperature of the titanium alloy of the workpiece (72), the workpiece 24 being within the α+β phase region of the titanium alloy of the workpiece. Heating (73) to a workpiece forging temperature within the piece forging temperature range, and high strain rate MAF (74) the workpiece, the high strain rate MAF (74) being used for different spacer heights. Includes press forging reduction with respect to the orthogonal axis of the piece. In a non-limiting embodiment of a multi-axis forging (74) according to the present disclosure, the workpiece 24 is press forged (75) to a primary reduction spacer height on a first orthogonal axis (A-axis). As used herein, the phrase "press-forged to a major reduction spacer height" refers to a workpiece that is oriented along a perpendicular axis to a desired final dimension of the workpiece along a particular orthogonal axis. It means to press forge. Therefore, the term "primary reduction spacer height" is defined as the spacer height used to obtain the final dimension of the workpiece along each orthogonal axis. All press forging steps to the main reduction spacer height should occur using a strain rate sufficient to adiabatically heat the interior region of the workpiece.

After press forging (75) the workpiece 24 in the direction of the first orthogonal A-axis to the primary reduction spacer height as shown in FIG. 3( a ), the process (70) optionally includes thermal insulation of the workpiece. The method further includes cooling the internally heated interior region (not shown) to a temperature at or near the workpiece forging temperature (step 76 shown in Figure 3(b)). The internal zone cooling time may range, for example, from 5 seconds to 120 seconds, 10 seconds to 60 seconds, or 5 seconds to up to 5 minutes, and the cooling time required depends on the size, shape of the workpiece. , And composition, and the nature of the environment around the workpiece will be recognized by those skilled in the art.

During the optional internal zone cooling period, aspects of the thermal management system 33 according to non-limiting embodiments disclosed herein allow the outer surface area 36 of the workpiece 24 to be at or near the temperature of the workpiece forging temperature. Heating up to (step 77). In this way, the temperature of the workpiece 24 is at or near uniform and is substantially isothermal to or near the workpiece forging temperature prior to each high strain rate MAF hit. Maintained. In certain non-limiting embodiments where the adiabatically heated interior region is allowed to cool for a particular interior region cooling time and the thermal management system 33 is used to heat the outer surface region 36, the temperature of the workpiece Returns to a temperature at or near the substantially uniform workpiece forging temperature, intermediate each of the A, B, and C forging hits. In another non-limiting embodiment according to the present disclosure, where the adiabatically heated interior region is cooled for a particular interior region cooling time and the outer surface region 36 is heated using the thermal management system 33, The temperature of the workpiece returns to a substantially uniform temperature within the workpiece forging temperature range, midway between each of the A, B, and C forging hits.

In a non-limiting embodiment, heating (77) the outer surface area 36 of the workpiece 24 may be accomplished using one or more outer surface heating features 38 of the thermal management system 33. Examples of possible outer surface heating features 38 include a flame heater adapted for flame heating of the workpiece 24, an induction heater adapted for induction heating, and a radiant heater adapted for radiant heating. , But not limited to these. Other mechanisms and techniques for heating the outer surface region of the workpiece will be apparent to those of ordinary skill in the art in view of this disclosure, and such features and techniques are within the scope of the disclosure. A non-limiting embodiment of the outer surface area heating mechanism 38 may include a box furnace (not shown). The box furnace uses, for example, one or more of a flame heating mechanism, a radiant heating mechanism, an induction heating mechanism, and/or any other suitable heating mechanism now or in the future known to those skilled in the art. It may be configured with various heating mechanisms for heating the outer surface area of the piece.

In another non-limiting embodiment, the temperature of the outer surface region 36 of the workpiece 24 is heated (34) using one or more die heaters 40 of the thermal management system 33 to the workpiece forging temperature. At or near that temperature, it can be maintained within the workpiece forging temperature range. The die heater 40 can be used to maintain the die 42 or the die press forging surface 44 of the die at or near the workpiece forging temperature, or within the workpiece forging temperature range. In a non-limiting embodiment, the thermal management system die 42 is heated to a temperature within a range that includes a workpiece forging temperature to a temperature below the workpiece forging temperature of 100°F (55.6°C). The die heater 40 is any suitable heating mechanism known to those skilled in the art now or in the future, including, but not limited to, a flame heating mechanism, a radiant heating mechanism, a conduction heating mechanism, and/or an induction heating mechanism. May heat the die 42 or die press forged surface 44. In a non-limiting embodiment, the die heater 40 may be a component of a box furnace (not shown). Although the thermal management system 33 is shown to be placed and used during the cooling step of the multi-axis forging process, the thermal management system 33 may or may not be placed during the press forging step. It is recognized as good.

In a non-limiting embodiment, after press forging (75) to the primary reduction spacer height on the A-axis (see FIG. 3), sometimes referred to herein as reduction “ A ”, and also applied. If so, subsequent press forging to the blanking down spacer height, which may include optional heating and cooling steps, after the optional cooling allowance (76) and heating (77) steps, " Applied on the B and C axes to "square-up". The phrase "press forging to a blanking reduction spacer height..." is otherwise press forging to the first roughing reduction spacer height ((78), (87), (96)). , And second roughing blanking spacers ((81), (90), (99)) are referred to herein as press forging, and any surface after press forging to the primary blanking spacer height. Defined as a press forging step used to reduce or "square" the expansion that occurs near the center. Expansion at or near the center of any face results in a triaxial stress state being introduced at that face, which can lead to cracking of the workpiece. The steps of press forging to a first reduction spacer height and press roughing to a second roughing reduction spacer height are referred to herein as a first roughing reduction, a second roughing reduction, or simply a roughing reduction. Also referred to as stamping, used to deform an inflated surface so that the surface of the workpiece is flat or substantially flat before the next press forging to the primary draft spacer height along the orthogonal axis. To be Roughing reduction includes press forging to a spacer height greater than the spacer height used in each step of press forging to the primary reduction spacer height. The strain rates under all first and second blanking pressures disclosed herein may be sufficient to adiabatically heat the interior region of the workpiece, but in non-limiting embodiments, The total strain that occurs under the first and second blanking pressures may not be sufficient to heat the workpiece significantly adiabatically, so the thermal insulation during the first and second roughing compressions The physical heating may not occur. Since the rough draft is performed at a spacer height greater than that used in press forging to the primary draft spacer height, the strain applied to the workpiece under the rough draft will insulate the internal area of the workpiece. May not be sufficient to heat the material. As can be seen, the incorporation of the first and second blanking pressures in the high strain rate MAF process, in a non-limiting embodiment, of at least one cycle consisting of A- B-C- B- C-A- C . Resulting in a sequence of forgings, A , B , and C including press forging to a primary draft spacer height, B, C, C, and A to a first or second rough draft blank spacer height. the method comprising pressing forging, or in another non-limiting embodiment, resulted in a -B-C- B -C-A- C consisting -A-B at least one cycle sequence of forging, a, B , and C include press forging to the primary draft spacer height, and B, C, C, A, A, and B press forging to the first or second rough blanking spacer height. including.

Referring again to FIGS. 3 and 5, in a non-limiting embodiment, after a press forging step (75) ( A reduction) to the primary reduction spacer height on the first orthogonal axis, and when applied, After allowing optional cooling (76) and heating (77) steps, the workpiece is press forged (78) on the B-axis to a first blanking reduction spacer height, as described above. The strain rate under the first roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the strain that occurs under the first roughing pressure is the work piece. Adiabatic heating during the first blanking pressure may not occur because it may not be sufficient to heat the piece significantly adiabatically. Optionally, the adiabatically heated interior region of the workpiece is cooled (79) to a temperature at or near the workpiece forging temperature, while the outer surface region of the workpiece is at or near the workpiece forging temperature. Heated to near temperature (80). All cooling times and heating methods for A reduction (75) disclosed above and in other embodiments of the present disclosure allow steps (79) and (80), as well as cooling of the interior region of the workpiece, It is applicable to all optional subsequent steps of heating the outer surface area.

The workpiece is then press forged (81) on the C-axis to a second roughing reduction spacer height that is greater than the main reduction spacer height. The first and second blanking reductions are applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the second roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the strain that occurs under the second roughing pressure is Adiabatic heating during the second blanking pressure may not occur because it may not be sufficient to heat the piece significantly adiabatically. Optionally, the adiabatically heated interior region of the workpiece is cooled (82) to a temperature at or near the workpiece forging temperature, while the outer surface region of the workpiece is at or near the workpiece forging temperature. Heated to near temperature (83).

The workpiece is then press forged in the direction of the second orthogonal axis, or B-axis, to the primary reduction spacer height (84). Press forging (84) to the primary reduction spacer height on the B axis is referred to herein as B reduction. After B reduction (84), optionally, the adiabatically heated interior region of the workpiece is cooled (85) to a temperature at or near the workpiece forging temperature, while the outer surface region of the workpiece is It is heated (86) to or near the piece forging temperature.

The workpiece is then press forged on the C-axis to a first roughing reduction spacer height greater than the main reduction spacer height (87). The strain rate under the first roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the strain that occurs under the first roughing pressure is Adiabatic heating during the first blanking pressure may not occur because it may not be sufficient to heat the piece significantly adiabatically. Optionally, the workpiece is cooled to or near the forging temperature (88), while the outer surface area of the workpiece is heated (89) to or near the workpiece forging temperature.

The workpiece is then press forged on the A-axis to a second roughing reduction spacer height greater than the main reduction spacer height (90). The first and second blanking reductions are applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the second roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the strain that occurs under the second roughing pressure is Adiabatic heating during the second blanking pressure may not occur because it may not be sufficient to heat the piece significantly adiabatically. Optionally, the adiabatically heated interior region of the workpiece is cooled (91) to a temperature at or near the workpiece forging temperature, while the outer surface region of the workpiece is at or near the workpiece forging temperature. Heated to near temperature (92).

The workpiece is then press forged in the direction of the third orthogonal axis, or C-axis, to the primary reduction spacer height (93). Press forging (93) to the primary reduction spacer height on the C-axis is referred to herein as C reduction. After C reduction (93), optionally, the adiabatically heated interior region of the workpiece is cooled (94) to a temperature at or near the workpiece forging temperature, while the outer surface region of the workpiece is It is heated to a temperature at or near the piece forging temperature (95).

The workpiece is then press forged on the A-axis to a first roughing reduction spacer height that is greater than the main reduction spacer height (96). The strain rate under the first roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the strain that occurs under the first roughing pressure is Adiabatic heating during the first blanking pressure may not occur because it may not be sufficient to heat the piece significantly adiabatically. Optionally, the adiabatically heated interior region of the workpiece is cooled (97) to a temperature at or near the workpiece forging temperature, while the outer surface region of the workpiece is at or near the workpiece forging temperature. Heated to near temperature (98).

The workpiece is then press forged on the B-axis to a second roughing reduction spacer height greater than the main reduction spacer height (99). The first and second blanking reductions are applied to substantially return the workpiece to the pre-forged shape of the workpiece. The strain rate under the second roughing pressure may be sufficient to adiabatically heat the interior region of the workpiece, but in a non-limiting embodiment, the strain that occurs under the second roughing pressure is Adiabatic heating during the second blanking pressure may not occur because it may not be sufficient to heat the piece significantly adiabatically. Optionally, the adiabatically heated interior region of the workpiece is cooled (100) to a temperature at or near the workpiece forging temperature, while the outer surface region of the workpiece is at or near the workpiece forging temperature. Heated to near temperature (101).

Referring to FIG. 5, in a non-limiting embodiment, press forging steps (75), (78), (81), (84), (87), (90), (93), (96), and One or more of (99) is repeated (102) until a total strain of at least 1.0 is achieved in the titanium alloy workpiece. In another non-limiting embodiment, the press forging steps (75), (78), (81), (84), (87), (90), (93), (96), and (99). One or more of these are repeated (102) until a total strain in the titanium alloy workpiece of at least 1.0 and up to less than 3.5 is achieved. At least 1.0 desired in any of the press forging steps (75), (78), (81), (84), (87), (90), (93), (96), and (99). Strain, or, alternatively, after achieving the desired strain in the range of at least 1.0 up to less than 3.5, an optional intermediate equilibration step (ie, cooling the interior region of the workpiece). Heating (76), (79), (82), (85), (88), (91), (94), (97), or (100), and the outer surface of the workpiece (77). , (80), (83), (86), (89), (92), (95), (98), or (101)) is not required and the workpiece may be cooled to ambient temperature. It will be appreciated. In a non-limiting embodiment, cooling comprises a liquid quench, such as a water quench. In another non-limiting embodiment, cooling comprises air cooling or cooling with a faster cooling rate.

The process described above includes a repeating sequence of press forging to the primary reduction spacer height, followed by press forging to the first and second roughing reduction spacer heights. A sequence of forgings representing one total MAF cycle as disclosed in the above non-limiting embodiments can be expressed as: A- B-C- B- C-A- C- A-B and has the formula Medium and underlined bold reductions (hits) are press forgings to the main reduction spacer height, and underlined or non-bold reductions are the first or second roughing reductions. All press forging reductions of the MAF process according to the present disclosure, including the main reduction spacer height and the press forging to the first and second roughing reductions, are sufficient to adiabatically heat the interior region of the workpiece. High strain rates, such as, but not limited to, strain rates in the range of 0.2 sec ^{-1 to} 0.8 sec ^-1 , or 0.2 sec ^{-1 to} 0.4 sec ^-1. It will be understood that it is implemented in. It is also understood that adiabatic heating may not occur substantially during the first and second roughing reductions due to the lower degree of deformation in these reductions as compared to the main reductions. Let's do it. Also, as an optional step, the intermediate continuous press forging reduction causes the adiabatically heated interior region of the workpiece to cool to a temperature at or near the workpiece forging temperature, and the outer surface of the workpiece is It will also be appreciated that the heat management system disclosed in the publication may be utilized to heat the workpiece to temperatures at or near the forging temperature. It is believed that these optional steps may be more beneficial when the method is used on larger size workpieces. Further, embodiments of the A- B-C- B- C-A- C- A-B forging sequence described herein include at least 1.0, or at least 1.0 and up to 3.5. It is understood that it may be repeated in whole or in part until a total strain in the range of less than is achieved in the workpiece.

Expansion in the workpiece results from the combination of surface die locks and the presence of hotter material near the center of the workpiece. As the expansion increases, the center of each face is progressively subjected to triaxial loading which can initiate crack initiation. In the sequence A-B-C- B- C-A- C- A-B, the use of rough stamping between each press forging to the primary draft spacer height reduces the tendency for crack formation in the workpiece. .. In a non-limiting embodiment, when the workpiece is in the shape of a cube, the first roughing reduction spacer height for the first roughing reduction is 40-60% greater than the main reduction spacer height. It may be for height. In a non-limiting embodiment, if the workpiece is in the shape of a cube, the second roughing reduction spacer height for the second roughing reduction is 15-30% greater than the main reduction spacer height. It may be for height. In another non-limiting embodiment, the first blanking reduction spacer height can be substantially equal to the second roughing reduction spacer height.

In a non-limiting embodiment of a thermally controlled high strain rate multi-axis forging according to the present disclosure, after a total strain in the range of at least 1.0, or at least 1.0 and up to 3.5, the workpiece is It has an average alpha particle size of 4 μm or less, which is considered the ultrafine grain (UFG) size. In a non-limiting embodiment according to the present disclosure, the application of at least 1.0, or at least 1.0 and a total strain in the range of up to less than 3.5 produces equiaxed grains.

In a non-limiting embodiment of the process according to the present disclosure, including multi-axis forging and the use of an optional thermal management system, the contact surface of the workpiece press die is a lubricant known to those of ordinary skill in the art, such as, but not limited to, a lubricant. , Graphite, glass, and/or other known solid lubricants and the like.

In certain non-limiting embodiments of the methods according to the present disclosure, the workpiece comprises a titanium alloy selected from α+β titanium alloys and metastable β titanium alloys. In another non-limiting embodiment, the workpiece comprises an α+β titanium alloy. In yet another non-limiting embodiment, the workpiece comprises a metastable beta titanium alloy. In a non-limiting embodiment, titanium alloys treated by the method according to the present disclosure include effective alpha phase precipitation and growth rates that are slower than those of Ti-6-4 alloy (UNS R56400), such rates including: Sometimes referred to herein as a "slower alpha velocity." In a non-limiting embodiment, the slower α-velocity is such that the diffusivity of the slowest diffusion alloying species in the titanium alloy is greater than the diffusivity of aluminum in the Ti-6-4 alloy at the β transus temperature (T _β ). Also achieved when late. For example, the Ti-6-2-4-2 alloy has a slower α than the Ti-6-4 alloy as a result of the presence of additional grain pinning elements in the Ti-6-2-4-2 alloy such as silicon. Indicates speed. Also, the Ti-6-2-4-6 alloy is better than the Ti-6-4 alloy as a result of the presence of additional β-stabilizing alloying additives such as higher molybdenum content than the T-6-4 alloy. Also has a slow α velocity. The result of the slower α-rate in these alloys is that β-annealing Ti-6-2-4-6 and Ti-6-2-4-2 alloys prior to high strain rate MAF indicates that Ti-6-2 -4-6 and Ti-6-2-4-2 are relatively fine and stable compared to Ti-6-4 alloys and certain other titanium alloys that exhibit faster α-phase precipitation and growth rates. That is, it produces a α-las size and a fine β-phase structure. The phrase "slower α-rate" is described in more detail above in this disclosure. Exemplary titanium alloys that may be processed using embodiments of the method according to the present disclosure include Ti-6-2-4-2 alloy, Ti-6-2-4-6 alloy, ATI 425®. Alloys (Ti-4Al-2.5V alloys), Ti-6-6-2 alloys, and Ti-6Al-7Nb alloys are included, but are not limited to.

In a non-limiting embodiment of the method according to the present disclosure, the β-annealing is sufficient to heat the workpiece to a β-annealing temperature and to form the 100% titanium β-phase microstructure in the workpiece. Holding the beta annealing temperature for a different annealing time and directly cooling the workpiece to a temperature at or near the workpiece forging temperature. In certain non-limiting embodiments, the β-annealing temperature is a temperature within a range of the β-transus temperature of the titanium alloy to a temperature above the β-transus temperature of the titanium alloy by up to 300°F (166.7°C). Non-limiting embodiments include beta annealing times of 5 minutes to 24 hours. One of ordinary skill in the art, upon reading this description, other β-annealing temperatures and β-annealing times are within the scope of the embodiments of the present disclosure, and, for example, relatively large workpieces may have 100% β-phase titanium microstructure. It will be appreciated that relatively higher β-annealing temperatures and/or longer β-annealing times may be required to form the.

In certain non-limiting embodiments in which the workpiece is held at the β-annealing temperature to form a 100% β-phase microstructure, the workpiece can also include the workpiece at or near the workpiece forging temperature or ambient temperature. Prior to cooling to temperature, it may be plastically deformed at the plastic deformation temperature in the β phase region of the titanium alloy. Plastic deformation of the workpiece can include at least one of stretching the workpiece, upsetting, and multiaxially forging at a high strain rate. In a non-limiting embodiment, plastic deformation in the beta phase region comprises upset forging the workpiece to a beta upset strain in the range of 0.1-0.5. In certain non-limiting embodiments, the plastic deformation temperature is within a temperature range that includes a β-transus temperature of a titanium alloy to a temperature that is up to 300°F (166.7°C) above the β-transus temperature of a titanium alloy.

FIG. 6 is a temperature-time thermomechanical process diagram for a non-limiting method of plastically deforming a workpiece above the β transus temperature and directly cooling to the workpiece forging temperature. In FIG. 6, the non-limiting method 200 illustrates a workpiece including a titanium alloy having a slower α precipitation and growth rate than that of a Ti-6-4 alloy, eg, β above the β transus temperature 206 of the titanium alloy. This includes heating 202 to an annealing temperature 204 and holding or "soaking" 208 the workpiece at a β annealing temperature 204 to form an all β titanium phase microstructure within the workpiece. In a non-limiting embodiment according to the present disclosure, after soaking 208, the workpiece may be plastically deformed 210. In a non-limiting embodiment, plastic deformation 210 comprises upset forging. In a non-limiting embodiment, plastic deformation 210 comprises upset forging to a true strain of 0.3. In a non-limiting embodiment, plastic deformation 210 includes thermally controlled high strain rate multi-axis forging (not shown in FIG. 6) at a β-annealing temperature.

Referring also to FIG. 6, after plastic deformation 210 in the β phase region, in a non-limiting embodiment, the workpiece is cooled 212 to the workpiece forging temperature 214 in the α+β phase region of the titanium alloy 212. In a non-limiting embodiment, cooling 212 includes air cooling or cooling at a faster rate than that achieved through air cooling. In another non-limiting embodiment, the cooling comprises a liquid quench, including, but not limited to, a water quench. After cooling 212, the workpiece is multi-axis forged 214 at high strain rate according to certain non-limiting embodiments of the present disclosure. In the non-limiting embodiment of FIG. 6, the workpiece is hit or press forged 12 times, that is, the three orthogonal axes of the workpiece are each non-sequentially press forged a total of 4 times. In other words, referring to FIGS. 2 and 6, the cycle comprising steps (a)-(optional b), (c)-(optional d), and (e)-(optional f) is It is carried out four times. In the non-limiting embodiment of FIG. 6, after a sequence of multi-axis forging including 12 hits, the total strain may be, for example, equal to at least 1.0, or at least 1.0 to a maximum of 3. It may be within the range of less than 5. After multi-axis forging 214, the workpiece is cooled 216 to ambient temperature. In a non-limiting embodiment, cooling 216 includes air cooling or cooling at a faster rate than that achieved through air cooling, although other forms of cooling such as, but not limited to, fluid or liquid quenching are described herein. Within the scope of the embodiments disclosed herein.

Non-limiting aspects of the present disclosure include high strain rate multiaxial forging at two temperatures in the α+β phase region. FIG. 7 illustrates multi-axis forging a titanium alloy workpiece at a first workpiece forging temperature and, optionally, utilizing the thermal management feature non-limiting embodiments disclosed herein above. , Cooling to a second workpiece forging temperature in the α+β phase, multi-axially forging a titanium alloy workpiece at the second workpiece forging temperature, and optionally, thermal management features disclosed herein. FIG. 3 is a temperature-time thermomechanical process diagram for a non-limiting method according to the present disclosure, including utilizing the non-limiting embodiment of FIG.

In FIG. 7, a non-limiting method 230 according to the present disclosure heats a workpiece 232 to a beta anneal temperature 234 above the beta transus temperature 236 of the alloy, and 232 the workpiece to a total beta in the titanium alloy workpiece. Holding or soaking 238 at β-annealing temperature 234 to form a phase microstructure. After soaking 238, the workpiece may be plastically deformed 240. In a limited embodiment, plastic deformation 240 comprises upset forging. In another non-limiting embodiment, plastic deformation 240 comprises upset forging to a strain of 0.3. In yet another non-limiting embodiment, the plastic deformation 240 of the workpiece comprises high strain multiaxial forging (not shown in FIG. 7) at a β-annealing temperature.

Referring also to FIG. 7, after plastic deformation 240, in the β phase region, the workpiece is cooled 242 to a first workpiece forging temperature 244 in the α+β phase region of the titanium alloy. In a non-limiting embodiment, the cooling 242 comprises one of air cooling or liquid quenching. After cooling 242, the workpiece is multi-axis forged 246 at a high strain rate at a first workpiece forging temperature 246, optionally using a thermal management system according to non-limiting embodiments disclosed herein. In the non-limiting embodiment of FIG. 7, the workpiece is 12 hits or press forged at the first workpiece forging temperature, with 90° rotation between each hit, ie, 3 of the workpieces. The orthogonal axis is press-forged four times each. In other words, referring to FIG. 2, the cycle including steps (a)-(optional b), (c)-(optional d), and (e)-(optional f) is 4 cycles. It is carried out once. In the non-limiting embodiment of FIG. 7, after high strain rate multi-axis forging 246 of the workpiece at the first workpiece forging temperature, the titanium alloy workpiece is second workpiece forging temperature 250 in the α+β phase region. Cooled to 248. After cooling 248, the workpiece is multi-axially forged at a high strain rate at a second workpiece forging temperature 250, optionally using a thermal management system according to non-limiting embodiments disclosed herein. In the non-limiting embodiment of FIG. 7, the workpiece is hit or press forged a total of 12 times at the second workpiece forging temperature. The number of hits applied to the titanium alloy workpiece at the first and second workpiece forging temperatures can vary depending on the desired true strain and the desired final grain size, and a suitable number of hits is It will be appreciated that it can be determined without undue experimentation in light of the present disclosure. After multi-axis forging 250 at the second workpiece forging temperature, the workpiece is cooled 252 to ambient temperature. In a non-limiting embodiment, the cooling 252 comprises one of air cooling to ambient temperature and liquid quenching.

In a non-limiting embodiment, the first workpiece forging temperature is 100° F. (55.6° C.) or more below the β-transus temperature of the titanium alloy to 500° F. (277. 8° C.) below the first workpiece forging temperature range, ie, the first workpiece forging temperature T ₁ is within the range of T _β −100° F>T ₁ ≧T _β −500° F. Is. In a non-limiting embodiment, the second workpiece forging temperature is 200°F (277.8°C) or more below the β-transus temperature of the titanium alloy to 700°F (388.T) of the β-transus temperature of the titanium alloy. 9° C.) below the second workpiece forging temperature range, that is, the second workpiece forging temperature T ₂ is within the range of T _β −200° F>T ₂ ≧T _β −700° F. Is. In a non-limiting embodiment, the titanium alloy workpiece comprises Ti-6-2-4-2 alloy, the first workpiece temperature is 1650° F. (898.9° C.), and the second workpiece temperature is The workpiece forging temperature is 1500°F (815.6°C).

FIG. 8 shows a work piece comprising a titanium alloy plastically deformed above the β transus temperature and cooled to the work piece forging temperature while at the same time subjecting the work piece to high strain heat management. FIG. 4 is a temperature-time thermomechanical process diagram of an embodiment of a non-limiting method according to the present disclosure for using speed multi-axis forging. In FIG. 8, a non-limiting method 260 using thermally controlled high strain rate multi-axis forging for grain refinement of a titanium alloy is shown in which a workpiece has a β annealing temperature above the β transus temperature 266 of the titanium alloy. Heating 262 to 264 and holding or soaking the workpiece at a β-annealing temperature 264 to form a full β-phase microstructure in the workpiece 268. After soaking 268 the workpiece at the β annealing temperature, the workpiece is plastically deformed 270. In a non-limiting embodiment, plastic deformation 270 can include thermally controlled high strain rate multiaxial forging. In a non-limiting embodiment, the workpiece is repeatedly strained using an optional thermal management system as disclosed herein as the workpiece cools through the β transus temperature. 272 multi-axis forged at speed. Although FIG. 8 shows three intermediate high strain rate multiaxial forging 272 steps, it is understood that more or less intermediate high strain rate multiaxial forging 272 steps may be present, if desired. Let's do it. The intermediate high strain rate multiaxial forging 272 step is intermediate between the initial high strain rate multiaxial forging step 270 at soaking temperature and the final high strain rate multiaxial forging step in the α+β phase region 274 of the titanium alloy. FIG. 8 shows one final high strain rate multi-axis forging step in which the temperature of the workpiece remains entirely within the α+β phase region, but reading this description, multiple multi-axis forging steps may be It will be appreciated that it may be carried out within the α+β phase region for grain refinement. According to non-limiting embodiments of the present disclosure, the at least one final high strain rate multiaxial forging step is performed entirely at a temperature within the α+β phase region of the titanium alloy workpiece.

Since the multi-axis forging steps 270, 272, 274 are performed as the temperature of the workpiece cools through the β-transus temperature of the titanium alloy, method embodiments such as those shown in FIG. This is referred to herein as "high strain rate multi-axis forging through β transus". In a non-limiting embodiment, the thermal management system (33 in FIG. 3) passes through each β transus forging temperature to maintain a uniform or substantially uniform temperature of the workpiece before each hit. And optionally in multi-axis forging through beta transus to reduce the cooling rate. After the final multi-axis forging 274 at the workpiece forging temperature in the α+β phase region, the workpiece is cooled 276 to ambient temperature. In a non-limiting embodiment, cooling 276 includes air cooling.

A non-limiting embodiment of a multi-axis forging using a thermal management system as disclosed herein above is a titanium alloy work piece having a cross-section greater than 4 square inches using conventional forging press equipment. It can be used to process pieces and the size of cubic shaped workpieces can be scaled to fit the capabilities of individual presses. It has been determined that alpha lamellas or laths from beta annealed structures readily disintegrate into uniform alpha grains at the workpiece forging temperatures disclosed in the non-limiting embodiments herein. It has also been determined that reducing the workpiece forging temperature reduces the size (particle size) of the alpha particles.

While not wishing to be bound by any particular theory, the grain refinement that occurs in the non-limiting embodiment of thermally controlled high strain rate multi-axis forging according to the present disclosure is a meta-dynamic restructuring. It is thought to occur through crystals. In prior art low strain rate multi-axis forging processes, dynamic recrystallization occurs instantaneously during the application of strain to the material. In high strain rate multi-axis forging according to the present disclosure, metadynamic recrystallization is believed to occur at the end of each deformation or forging hit while at least the interior region of the workpiece is hot due to adiabatic heating. The residual adiabatic heat, internal zone cooling time, and external surface zone heating affect the extent of grain refinement in the non-limiting method of thermally controlled high strain rate multiaxial forging according to the present disclosure.

The inventors have further developed an alternative method according to the present disclosure that provides certain benefits with respect to the above processes, including multi-axis forging as well as the use of thermal management systems and cubic shaped workpieces containing titanium alloys. .. (1) Cube workpiece geometry used in certain embodiments of the thermally controlled multi-axis forging disclosed herein, (2) die chilling (ie die temperature, It is believed that one or more of lowering the workpiece forging temperature significantly below) and (3) using a high strain rate may undesirably concentrate strain within the core region of the workpiece. ..

Alternative methods according to the present disclosure can achieve generally uniform fine, fine, or ultrafine grain sizes across billet-sized titanium alloy workpieces. In other words, the workpieces processed by such alternative methods may include a desired grain size, such as ultra-fine grained microstructure, throughout the workpiece, not just in the central region of the workpiece. A non-limiting embodiment of such an alternative method includes a "multiple upsetting and stretching" step performed on a billet having a cross section greater than 4 square inches. The multiple upsetting and drawing steps are intended to impart a uniform fine-grained, fine-grained, or ultrafine-grained microstructure throughout the workpiece while substantially preserving the original dimensions of the workpiece. It These alternative methods are referred to herein as “MUD” method embodiments because they include multiple upset and draw steps. The MUD method involves severe plastic deformation and can produce uniform ultrafine grains in billet size (eg, 30 inch (76.2 cm) long) titanium alloy workpieces. In a non-limiting embodiment of the MUD method according to the present disclosure, the strain rates used for the upset forging and stretch forging steps are in the range of 0.001 sec ^{−1 to} 0.02 sec ⁻¹ . In contrast, the strain rates typically used in conventional free upset and draw forging are in the range of 0.03 sec ^{−1 to} 0.1 sec ⁻¹ . Strain rates for MUDs are slow enough to prevent adiabatic heating of the work piece and to keep the forging temperature under control, but strain rates are still acceptable for commercial practice.

A schematic diagram of a non-limiting embodiment of the MUD method is provided in FIG. 9, and a flow chart of a particular embodiment of the MUD method is provided in FIG. With reference to FIGS. 9 and 10, a non-limiting method 300 for refining grains in a titanium alloy-containing workpiece using multiple upset and draw forging steps is described as an elongated titanium alloy workpiece 302. To a workpiece forging temperature within the α+β phase region of the titanium alloy. In a non-limiting embodiment, the shape of the elongated workpiece is a cylinder or cylinder-like shape. In another non-limiting embodiment, the shape of the workpiece is an octagonal cylinder or a regular octagon.

The elongated workpiece has a starting cross sectional dimension. For example, in a non-limiting embodiment of the MUD method according to the present disclosure where the starting workpiece is a cylinder, the starting cross-sectional dimension is the diameter of the cylinder. In a non-limiting embodiment of the MUD method according to the present disclosure in which the starting workpiece is an octagonal cylinder, the starting cross sectional dimension is the diameter of the circumscribed circle of the octagonal cross section, ie, the circle passing through all vertices of the octagonal cross section. Is the diameter of.

When the elongated workpiece is at the workpiece forging temperature, the workpiece is upset 304. After upset forging 304, in a non-limiting embodiment, the workpiece is rotated 90 degrees to orientation 306 and then subjected to multi-pass stretch forging 312. The actual rotation of the workpiece is arbitrary and the purpose of this step is to place the workpiece in the correct orientation (see Figure 9) with respect to the forging device for the subsequent multi-pass draw forging 312 step.

Multi-pass stretch forging involves rotating the workpiece incrementally (depicted by arrow 310) in the direction of rotation (indicated by the direction of arrow 310), and then stretch forging the workpiece after each increment of rotation. 312 is included. In a non-limiting embodiment, incremental rotation 310 and stretch forging 312 are repeated until the workpiece has a starting cross sectional dimension. In a non-limiting embodiment, the upset forging and multi-pass stretch forging steps are repeated until a total strain of at least 1.0 is achieved in the workpiece. Another non-limiting embodiment repeats the heating, upset forging, and multi-pass stretch forging steps until a total strain of at least 1.0 and up to less than 3.5 is achieved in the workpiece. including. In yet another non-limiting embodiment, the heating, upset forging, and multi-pass draw forging steps are repeated until a total strain of at least 10 is achieved in the workpiece. When a total strain of 10 is applied to the MUD forging, an ultrafine grained alpha microstructure is produced and increasing the total strain applied to the workpiece results in a smaller average grain size. is expected.

An aspect of the present disclosure is to use sufficient upsetting and strain rate during a multi-pass drawing step to result in severe plastic deformation of the titanium alloy workpiece, which, in non-limiting embodiments, is It further provides a fine particle size. In a non-limiting embodiment, the strain rate used in upset forging is in the range of 0.001 sec ^{−1 to} 0.003 sec ⁻¹ . In another non-limiting embodiment, the strain rate used in the multi-pass stretch forging step is in the range of 0.01 sec ^{-1 to} 0.02 sec ^-1 . Strain rates within these ranges do not result in adiabatic heating of the workpiece, which allows workpiece temperature control and is also found to be sufficient for economically acceptable commercial practice. Are disclosed in the '538 application.

In a non-limiting embodiment, after completion of the MUD method, the workpiece has substantially the original dimensions of the starting elongated article, eg, cylinder 314 or octagonal tube 316. In another non-limiting embodiment, after completion of the MUD method, the workpiece has substantially the same cross section as the starting workpiece. In a non-limiting embodiment, a single upsetting requires multiple stretch hits and intermediate rotations to bring the workpiece back into a shape that includes the starting cross section of the workpiece.

In a non-limiting embodiment of the MUD method in which the workpiece is in the shape of a cylinder, for example, incremental rotation and stretch forging may be performed until the cylindrical workpiece is rotated 360° and stretch forged in each increment. The method further comprises the steps of rotating the workpiece in increments of 15° and then draw forging. In a non-limiting embodiment of the MUD method in which the workpiece is in the shape of a cylinder, after each upset forging, there are 24 stretch forging steps with intermediate incremental rotation between successive stretch forging steps. To substantially its starting cross-sectional dimension. In another non-limiting embodiment in which the workpiece is in the shape of an octagonal cylinder, incremental rotation and stretch forging include cylindrical work until the cylindrical workpiece is rotated 360° and stretch forged in each increment. The method further includes the steps of stretch forging after rotating the piece in 45° increments. In a non-limiting embodiment of the MUD method, where the workpiece is in the shape of an octagonal cylinder, after each upset forge, eight forging steps separated by incremental rotation of the workpiece substantially initiates the workpiece. Used to make cross-sectional dimensions. It has been observed in a non-limiting embodiment of the MUD method that manipulation of the octagonal cylinder by the handling equipment is more accurate than manipulation of the cylinder by the handling equipment. Also, the operation of the octagonal tube with the handling equipment in the non-limiting embodiment of the MUD method used the hand tongs in the non-limiting embodiment of the thermally controlled high strain rate MAF process disclosed herein. It was also observed to be more accurate than the manipulation of cubic shaped workpieces. In view of this description, other stretch forging sequences, each including a number of draw forging steps and intermediate incremental rotations of a particular degree, have the following results. It will be appreciated that it may be used for other cross-section billet shapes, such that it is substantially the same as the starting shape of the workpiece in FIG. Such other possible sequences can be determined by one of ordinary skill in the art without undue experimentation and are within the scope of the present disclosure.

In a non-limiting embodiment of the MUD method according to the present disclosure, the workpiece forging temperature comprises a temperature within the workpiece forging temperature range. In a non-limiting embodiment, the workpiece forging temperature is 100° F (55.6° C.) below the β transus temperature (T _β ) of the titanium alloy to 700° F (388. 9°C) below the workpiece forging temperature range. In yet another non-limiting embodiment, the workpiece forging temperature is 300°F (166.7°C) below the β-transus temperature of the titanium alloy to 625°F (347°C) of the β-transus temperature of the titanium alloy. It is within the temperature range of the lower temperature. In a non-limiting embodiment, the lower end of the workpiece forging temperature range is α+β where no substantial damage occurs to the surface of the workpiece during a forging hit, as can be determined by one of ordinary skill in the art without undue experimentation. It is the temperature in the phase region.

In a non-limiting embodiment of the MUD method according to the present disclosure, a workpiece forging temperature range for a Ti-6-2-4-2 alloy having a β transus temperature (T _β ) of about 1820° F. (993.3° C.). May be, for example, 1120°F (604.4C) to 1720°F (937.8°C), or in another embodiment, 1195°F (646.1°C) to 1520°F (826). 7° C.).

Non-limiting embodiments of the MUD method include multiple iterative steps. In a non-limiting embodiment, the titanium alloy workpiece is heated to the workpiece forging temperature after upsetting the titanium alloy workpiece. In another non-limiting embodiment, the titanium alloy workpiece is heated to the workpiece forging temperature prior to the draw forging step of the multi-pass draw forging. In another non-limiting embodiment, the workpiece is heated after the upsetting or stretch forging step to optionally return the actual workpiece temperature to or near the workpiece forging temperature.

Embodiments of the MUD method have been determined to impart excessive deformation, also referred to as excess work or severe plastic deformation, aimed at creating ultra-fine grains within a workpiece containing titanium alloys. .. While not intending to be bound by any particular theory of operation, the circular or octagonal cross-sectional shapes of cylindrical and octagonal tubular workpieces, respectively, are square or rectangular in cross-section during the MUD method. It is believed that the strain is distributed more evenly over the workpiece cross-section than the workpiece. The detrimental effect of friction between the work piece and the forging die is also reduced by reducing the area of the work piece that contacts the die.

In addition, reducing the temperature during the MUD process was also determined to reduce the final particle size to a size that is characteristic of the particular temperature used. Referring to FIG. 10, in a non-limiting embodiment of a method 400 for refining the grain size of a workpiece, after the workpiece is processed by the MUD method at a workpiece forging temperature, the temperature of the workpiece is 416 that can be cooled to a second workpiece forging temperature. In a non-limiting embodiment, after cooling the workpiece to the second workpiece forging temperature, the workpiece is upset forged 418 at the second workpiece forging temperature. The workpiece is either rotated 420 or otherwise oriented with respect to the forging press for subsequent stretch forging steps. The workpiece is multi-step draw forged 422 at a second workpiece forging temperature. Multi-step stretch forging 422 at the second workpiece forging temperature includes incrementally rotating the workpiece 424 in the direction of rotation (see FIG. 9) and, at each second rotation increment, draw forging at the second workpiece forging temperature. What to do 426. In a non-limiting embodiment, the steps of upsetting, incremental rotation 424, and stretch forging are repeated 426 until the workpiece has a starting cross sectional dimension. In another non-limiting embodiment, the steps of upset forging 418, rotation 420, and multi-step draw forging 422 at the second workpiece temperature are at least 1.0, or 1.0 to a maximum of 3.5. Repeated until less than, or up to 10 or more total strains are achieved in the workpiece. It will be appreciated that the MUD method can continue until any desired total strain is applied to the titanium alloy workpiece.

In non-limiting embodiments, including embodiments of the multi-temperature MUD method, the workpiece forging temperature, or first workpiece forging temperature, is about 1600°F (871.1°C) and the second workpiece forging temperature is about 1600°F (871.1°C). The forging temperature is about 1500°F (815.6°C). Subsequent workpiece forging temperatures that are lower than the first and second workpiece forging temperatures, such as the third workpiece forging temperature, the fourth workpiece forging temperature, etc., are of non-limiting embodiments of the present disclosure. It is within the range.

With the progress of forging, grain refinement causes a decrease in flow stress at a fixed temperature. It was determined that reducing the forging temperature for successive upsetting and drawing steps kept the flow stress constant and increased the rate of refinement of the microstructure. In a non-limiting embodiment of a MUD according to the present disclosure, a total strain of at least 1.0, at least 1.0 and up to less than 3.5, or up to 10 is a uniform equiaxed within the titanium alloy workpiece. Providing an alpha ultrafine grained microstructure, and the lower temperature of the two-temperature (or multi-temperature) MUD process, can be a decisive factor in final grain size after up to 10 total strains have been applied to the MUD structure. Is expected.

Aspects of the present disclosure are that after treating a workpiece by the MUD method, the subsequent deformation step coarsens the refined grain size unless the temperature of the workpiece is subsequently heated above the β-transus temperature of the titanium alloy. Including the possibility that it will be implemented without any change. For example, in a non-limiting embodiment, the practice of subsequent deformation is MUD method followed by draw forging, multiple draw forging, upset forging, or of these forging techniques at temperatures within the α+β phase region of the titanium alloy. It may include any combination of two or more. In a non-limiting embodiment, the subsequent deforming or forging step determines the starting cross-sectional dimension of the cylindrical or other elongated workpiece to produce a uniform fine, fine grain, or ultra fine grain structure within the titanium alloy workpiece. Multi-pass stretch forging, upsetting while still maintaining and reducing to some fractional cross-sectional dimension, such as, but not limited to, one-half cross-sectional dimension, one-quarter cross-sectional dimension, etc. Includes a combination of forging and draw forging.

In a non-limiting embodiment of the MUD method, the workpiece comprises a titanium alloy selected from the group consisting of α+β titanium alloys and metastable β titanium alloys. In another non-limiting embodiment of the MUD method, the workpiece comprises α+β titanium alloy. In yet another non-limiting embodiment of the upset and draw processes disclosed herein, the workpiece comprises a metastable beta titanium alloy. In a non-limiting embodiment of the MUD method, the workpiece is a Ti-6-2-4-2 alloy, a Ti-6-2-4-6 alloy, an ATI 425® titanium alloy (Ti-4Al-. 2.5V), and a titanium alloy selected from Ti-6-6-2 alloy.

Prior to heating the workpiece to the workpiece forging temperature in the α+β phase region according to the MUD embodiments of the present disclosure, in a non-limiting embodiment, the workpiece is heated to the β annealing temperature and 100 times within the workpiece. It may be held at the β annealing temperature for a sufficient β annealing time to form the% β phase titanium microstructure and cooled to ambient temperature. In a non-limiting embodiment, the β-annealing temperature is within a β-annealing temperature range that includes a β-transus temperature of a titanium alloy to a temperature that is up to 300° F. (166.7° C.) above the β-transus temperature of a titanium alloy. In a non-limiting embodiment, the beta anneal time is 5 minutes to 24 hours.

In a non-limiting embodiment, the workpiece is a billet that is coated on all or certain surfaces with a lubricious coating that reduces friction between the workpiece and the forging die. In a non-limiting embodiment, the lubricious coating is a solid lubricant, such as, but not limited to, one of graphite and glass lubricants. Other lubricious coatings known to those skilled in the art now or in the future are within the scope of the present disclosure. In addition, in a non-limiting embodiment of the MUD method using a cylindrical or other elongated shaped workpiece, the contact area between the workpiece and the forging die is such that the cubic shaped workpiece is multi-axis forged. Is smaller than the contact area at. For example, for a 4 inch cube, two of all 4 inch by 4 inch faces of the cube will contact the die. For a 5 foot long billet, the billet length is larger than a typical 14 inch long die and the reduced contact area results in reduced die friction and more uniform titanium alloy workpiece microstructure and macros. Bring structure.

Prior to heating a workpiece comprising a titanium alloy to a workpiece forging temperature in the α+β phase region according to a MUD embodiment of the present disclosure, in a non-limiting embodiment, the workpiece comprises a 100% β phase in the titanium alloy. After being held for a β-annealing time sufficient to form the alloy and before the alloy is cooled to ambient temperature, it is plastically deformed at a plastic deformation temperature within the β-phase region of the titanium alloy. In a non-limiting embodiment, the plastic deformation temperature is equal to the β-annealing temperature. In another non-limiting embodiment, the plastic deformation temperature is within a plastic deformation temperature range that includes a β-transus temperature of a titanium alloy to a temperature that is up to 300°F (166.7°C) above the β-transus temperature of a titanium alloy. ..

In a non-limiting embodiment of the MUD method, plastic deformation of a workpiece in the beta phase region of a titanium alloy includes stretching the titanium alloy workpiece, upset forging, and multiaxially forging at a high strain rate. At least one of In another non-limiting embodiment, plastic deformation of the workpiece in the beta phase region of a titanium alloy comprises multiple upsetting and draw forging according to non-limiting embodiments of the present disclosure to forge the workpiece. Cooling to or near temperature includes air cooling. In yet another non-limiting embodiment, the plastic deformation of the work piece in the beta phase region of the titanium alloy causes the work piece to be upset by 30-35% under another dimension such as height or length. Including doing.

Another aspect of the MUD method of the present disclosure may include heating the forging die during forging. A non-limiting embodiment is a temperature range defined by a die of a forging furnace used to forge a workpiece at a temperature between workpiece forging temperature and 100°F (55.6°C) below the workpiece forging temperature. Including heating to an internal temperature.

In a non-limiting embodiment of the MUD method according to the present disclosure, the method for the production of ultrafine grained titanium alloy comprises selecting a titanium alloy having a slower α precipitation and growth rate than Ti-6-4 alloy. .Beta.-annealing the alloy to provide a fine, stable .alpha. Multi-axis forging at high strain rates. The titanium alloy may be selected from α+β titanium alloys and metastable β titanium alloys that provide a fine and stable α lath structure after β annealing.

It is believed that certain methods disclosed herein can also be applied to metals and metal alloys other than titanium alloys to reduce the grain size of workpieces of these alloys. Another aspect of the present disclosure includes non-limiting embodiments of methods for high strain rate multi-step forging of metals and metal alloys. A non-limiting embodiment of the method includes heating a workpiece that includes a metal or metal alloy to a workpiece forging temperature. After heating, the workpiece is forged at the workpiece forging temperature at a strain rate sufficient to adiabatically heat the interior region of the workpiece. After forging, a waiting period is used before the next forging step. During the waiting period, the temperature of the adiabatically heated interior region of the metal alloy workpiece is cooled to the workpiece forging temperature, while at least one surface region of the workpiece is heated to the workpiece forging temperature. Forging the workpiece and then heating at least one surface region of the metal alloy workpiece to the workpiece forging temperature while equilibrating the adiabatically heated interior region of the workpiece to the workpiece forging temperature comprises: , And so on until the desired property is obtained. In a non-limiting embodiment, forging includes one or more of press forging, upset forging, stretch forging, and roll forging. In another non-limiting embodiment, the metal alloy is selected from the group consisting of titanium alloys, zirconium and zirconium alloys, aluminum alloys, iron alloys, and superalloys. In yet another non-limiting embodiment, the desired property is one or more of applied strain, average grain size, shape, and mechanical properties. Mechanical properties include, but are not limited to, strength, ductility, fracture toughness, and hardness.

The following examples are intended to further illustrate certain non-limiting embodiments without limiting the scope of the invention. The person skilled in the art will understand that modifications of the following examples are possible within the scope of the invention, which is defined only by the claims.

Example 1 A bar of Ti-6-2-4-2 alloy is identified in the industry by specification number AMS4976, which is typically used to process Ti-6-2-4-2 alloy. Processed according to the commercial forging process. By looking at the specifications of AMS4976, those skilled in the art will understand the details of the processes for achieving the mechanical properties and microstructure described in the specifications. After treatment, the alloys were metallographically prepared and microstructured microscopically. As shown in the micrograph of the prepared alloy contained in FIG. 11( a ), the microstructure contains α-grains (light colored areas in the image) of about 20 μm or larger.

In accordance with non-limiting embodiments within the present disclosure, 4.0 inch cubic shaped Ti-6-2-4-2 alloy workpieces were β-annealed at 1950°F (1066°C) for 1 hour and then: Air cooled to ambient temperature. After cooling, the β-annealed cubic shaped workpiece was heated to a workpiece forging temperature of 1600°F (871.1°C) and forged using a 4-strain high strain rate MAF. The hits were the following sequence for the following orthogonal axes: ABCA. The hits were for a spacer height of 3.25 inches and the ram speed was 1 inch per second. There was no control of strain rate in the press, but for a 4.0 inch cube, this ram speed yields the lowest strain rate during a press of 0.25 sec ^-1 . The time between successive orthogonal hits was about 15 seconds. The total strain applied to the workpiece was 1.37. The microstructure of the Ti-6-2-4-2 alloy treated in this way is shown in the micrograph of Figure 11(b). The majority of alpha particles (light colored areas) are about 4 μm or less, which is substantially more than the alpha particles produced by the commercial forging process described above represented by the micrograph of FIG. 11( a ). Is fine.

Example 2 A bar of Ti-6-2-4-6 alloy was processed according to the commercial forging process typically used for T-6-2-4-6 alloy, ie according to specification AMS4981. By referring to the specification of AMS4981, those skilled in the art will understand the details of the process for achieving the mechanical properties and microstructure described in the specification. After treatment, the alloy was prepared metallographically and microstructured microscopically. As shown in the micrograph of the prepared alloy shown in FIG. 12( a ), the microstructure shows α-grains (light colored areas) of about 10 μm and above.

In a non-limiting embodiment according to the present disclosure, a 4.0 inch cubic shaped Ti-6-2-4-6 alloy workpiece is beta annealed at 1870°F (1066°C) for 1 hour and then Air cooled to ambient temperature. After cooling, the β-annealed cubic shaped workpiece was heated to a workpiece forging temperature of 1500°F (815.6°C) and forged using a 4-strain high strain rate MAF. The hits were the following sequence for the following orthogonal axes: ABCA. The hits were for a spacer height of 3.25 inches and the ram speed was 1 inch per second. There was no control of strain rate in the press, but for a 4.0 inch cube, this ram speed yields the lowest strain rate during a press of 0.25 sec ^-1 . The time between successive orthogonal hits was about 15 seconds. The total strain applied to the workpiece was 1.37. The microstructure of the alloy thus treated is shown in the micrograph in Figure 12(b). The majority of alpha particles (light colored areas) are about 4 μm or less, and in each case more than the alpha particles produced by the commercial forging process described above represented by the micrograph in FIG. 12( a ). It turns out that it is much finer.

Example 3 In a non-limiting embodiment according to the present disclosure, a 4.0 inch cubic shaped Ti-6-2-4-6 alloy workpiece is beta annealed at 1870°F (1066°C) for 1 hour. , Then air cooled. After cooling, the β-annealed cube-shaped workpiece was heated to a workpiece forging temperature of 1500°F (815.6°C) and a high strain rate MAF of 3 hits, one each on the A, B, and C axes. (I.e., the hit was the following sequence for the next orthogonal axis: ABC). The hits were for a spacer height of 3.25 inches and the ram speed was 1 inch per second. There was no control of strain rate in the press, but for a 4.0 inch cube, this ram speed yields the lowest strain rate during a press of 0.25 sec ^-1 . The time between successive orthogonal hits was about 15 seconds. After the A-B-C hit cycle, the workpiece was reheated to 1500°F (815.6°C) for 30 minutes. The cube was then subjected to high strain rate MAF with one hit on the A, B, and C axes, ie, the hit was of the following sequence with respect to the next orthogonal axis: ABC. The hits were for the same spacer height and used the same ram speed as used in the first ABC hit sequence. After the second sequence of ABC hits, the workpiece was reheated to 1500°F (815.6°C) for 30 minutes. The cube was then high strain rate MAF with one hit on each of the A, B, and C axes, ie, in the ABC sequence. The hits were for the same spacer height as in the first ABC hit sequence and the same ram speed and time between hits was used. This embodiment of the high strain rate multi-axis forging process applied a strain of 3.46. The microstructure of the alloy thus treated is shown in the micrograph of FIG. It can be seen that most of the α particles (light colored regions) are about 4 μm or less. The α-particles are composed of individual α-grains, and each of the α-grains has a particle size of 4 μm or less, and is considered to be likely to be equiaxed.

Example 4 In a non-limiting embodiment according to the present disclosure, a 4.0 inch cubic shaped Ti-6-2-4-2 alloy workpiece is beta annealed at 1950°F (1066°C) for 1 hour. , Then air cooled. After cooling, the β-annealed cubic shaped workpiece was heated to a workpiece forging temperature of 1700°F (926.7°C) and held for 1 hour. Two high strain rate MAF cycles (2 sequences of 3 ABC hits, 6 hits in total) were used at 1700°F (926.7°C). The time between successive hits was about 15 seconds. The sequence of forgings was an A hit to a 3 inch stop; a B hit to a 3.5 inch stop; and a C hit to a 4.0 inch stop. This forging sequence provides equal strain on all three orthogonal axes for every three-hit MAF sequence. The ram speed was 1 inch per second. There was no control of strain rate in the press, but for a 4.0 inch cube, this ram speed yields the lowest strain rate during a press of 0.25 sec ^-1 . The total strain per cycle is less than forging to 3.25 inch reduction in each direction, as in the previous examples.

The workpiece was reheated to 1650°F (898.9°C) and subjected to high strength MAF for 3 additional hits (ie, 1 additional ABC high strain rate MAF cycle). .. The sequence of forging was an A hit to a 3 inch stop; a B hit to a 3.5 inch stop; and a C hit to a 4.0 inch stop. The total strain applied to the workpiece after forging was 2.59.

The microstructure of the forged workpiece of Example 4 is shown in the micrograph of Figure 14. It can be seen that most of the α particles (light colored areas) are networked structures. The α-particles are composed of individual α-grains, and each of the α-grains has a particle size of 4 μm or less, and is considered to be likely to be equiaxed.

Example 5 In a non-limiting embodiment according to the present disclosure, a 4.0 inch cube shaped Ti-6-2-4-2 alloy workpiece is beta annealed at 1950°F (1066°C) for 1 hour. , Then air cooled. After cooling, the β-annealed cubic shaped workpiece was heated to a workpiece forging temperature of 1700°F (926.7°C) and held for 1 hour. Six press forgings ( A , B , C , A , B , C ) to the main reduction spacer height were applied to a cubic shaped workpiece using the MAF according to the present disclosure. In addition, during each press forging to a 3.25 inch primary reduction spacer height, first and second rough reductions were performed on the other axis to "square" the workpiece. .. The overall forging sequence used is as follows, the underlined bold hits are press forgings to the main draft spacer height: A- B-C- B- C-A- C- A. -B- A- B-C- B- C-A- C .

The sequence of forgings, including the primary, first rough, and second rough spacer height (inches) utilized, is outlined in the table below. The ram speed was 1 inch per second. There was no control of strain rate in the press, but for a 4.0 inch cube, this ram speed yields the lowest strain rate during a press of 0.25 sec ^-1 . The elapsed time between hits was about 15 seconds. The total strain after thermally managed MAF according to this non-limiting embodiment was 2.37.

The microstructure of the workpiece forged by the process described in this Example 5 is shown in the micrograph of FIG. It can be seen that most of the alpha particles (light colored areas) are elongated. The α-particles are composed of individual α-grains, and each of the α-grains has a particle size of 4 μm or less, and is considered to be likely to be equiaxed.

Example 6 In a non-limiting embodiment according to the present disclosure, a 4.0 inch cubic shaped Ti-6-2-4-2 alloy workpiece is beta annealed at 1950°F (1066°C) for 1 hour. , Then air cooled. In accordance with an embodiment of the present disclosure, a thermally managed high strain rate MAF comprising 6 hits (2 A-B-C MAF cycles) at 1900° C. on a workpiece with a 30 second hold between each hit. It was carried out in. The ram speed was 1 inch per second. There was no control of strain rate in the press, but for a 4.0 inch cube, this ram speed yields the lowest strain rate during a press of 0.25 sec ^-1 . A sequence of 6 hits with intermediate retention was designed to heat the surface of the piece through the β transus temperature during MAF, which can therefore be referred to as high strain rate MAF through transus. This process results in surface structure refinement and crack minimization during subsequent forging. The workpiece was then heated at 1650° F. (898.9° C.), ie below the β transus temperature for 1 hour. A MAF according to an embodiment of the present disclosure containing 6 hits (2 A-B-C MAF cycles) was applied to the workpiece with about 15 seconds between hits. The first 3 hits (the hits during the first A-B-C MAF cycle) were performed with a spacer height of 3.5 inches and the second 3 hits (the second A-B-C). Hits in C's MAF cycle) were performed using a spacer height of 3.25 inches. The workpiece was heated to 1650° F. between a 3.5 inch spacer hit and a 3.25 inch spacer hit and held for 30 minutes. The smaller reduction used for the first 3 hits (ie, the larger spacer height) was designed to prevent cracking, as smaller reductions collapse the boundary structure, which can lead to cracking. .. The workpiece was reheated to 1500°F (815.6°C) for 1 hour. MAF according to embodiments of the present disclosure was then applied using 3 ABC hits to 3.25 inch reduction (1 MAF cycle) with 15 seconds between each hit. .. This sequence of heavier reductions is designed to add additional work to non-boundary structures. The ram speed for all hits described in Example 6 was 1 inch per second.

A total strain of 3.01 was applied to the workpiece of Example 6. A representative photomicrograph of the center of the thermally controlled MAF workpiece of Example 6 is shown in Figure 16(a). A representative micrograph of the surface of the thermally controlled MAF workpiece of Example 6 is presented in Figure 16(b). The surface microstructure (FIG. 16(b)) is substantially refined, with the majority of particles and/or grains having a size of about 4 μm or less, which is an ultrafine grain microstructure. The central microstructure shown in FIG. 16( a) shows highly refined grains, the α grains are composed of individual α grains, and each of the α grains has a grain size of 4 μm or less. , It is highly likely that the shape is equiaxed.

It will be appreciated that this description illustrates embodiments of the invention that are related to a clear understanding of the invention. Certain aspects that are apparent to those of ordinary skill in the art and that therefore do not facilitate a better understanding of the present invention have not been presented to simplify the present description. Although only a limited number of embodiments of the present invention are necessarily described herein, one of ordinary skill in the art will appreciate that many modifications or variations of the present invention are possible in light of the above description. You will recognize. Such variations and modifications of the invention are intended to be covered by the foregoing description and the following claims.
[Aspect of the Invention]
[1] A method for reducing the particle size of a work piece containing a titanium alloy,
Β-annealing the workpiece,
Cooling the β-annealed workpiece to a temperature below the β-transus temperature of the titanium alloy;
Including multi-axis forging the workpiece, the multi-axis forging,
The workpiece at a strain rate sufficient to adiabatically heat the interior region of the workpiece in the direction of the first orthogonal axis of the workpiece at a workpiece forging temperature within the workpiece forging temperature range. Press forging,
Workpiece forging within the workpiece forging temperature range in the direction of the second orthogonal axis of the workpiece at a strain rate sufficient to adiabatically heat the workpiece in the interior region of the workpiece. Press forging at temperature,
Forging a workpiece within the workpiece forging temperature range in a direction of a third orthogonal axis of the workpiece at a strain rate sufficient to adiabatically heat the interior region of the workpiece. Press forging at temperature,
Repeating at least one of the press forging steps until a total strain of at least 1.0 is achieved in the workpiece.
[2] The method of [1], wherein at least one of the press forging steps is repeated until a total strain in the range of at least 1.0 up to less than 3.5 is achieved in the workpiece.
[3] The method of [1], wherein the strain rate used during press forging is in the range of 0.2 sec ^{−1 to} 0.8 sec ⁻¹ .
[4] The method of [1], wherein the workpiece comprises one of an α+β titanium alloy and a metastable β titanium alloy.
[5] The method of [1], wherein the workpiece contains an α+β titanium alloy.
[6] The titanium alloy comprises at least one of a grain pinning alloying additive and a β-stabilizing content effective to reduce α-phase precipitation and growth rate. Method.
[7] The workpiece is a Ti-6Al-2Sn-4Zr-6Mo alloy (UNS R56260), Ti-6Al-2Sn-4Zr-2Mo-0.08Si alloy (UNS R54620), Ti-4Al-2.5V alloy. The method of [1], including a titanium alloy selected from (UNS R54250), Ti-6Al-7Nb alloy (UNS R56700), and Ti-6Al-6V-2Sn alloy (UNS R56620).
[8] The method of [1], wherein cooling the β-annealed workpiece includes cooling the workpiece to ambient temperature.
[9] The method of [1], wherein cooling the β-annealed workpiece includes cooling the workpiece to a temperature at or near the workpiece forging temperature.
[10] β-annealing the workpiece may be performed within a temperature range of the workpiece from the β-transus temperature of the titanium alloy to the β-transus temperature of the titanium alloy at a maximum of 300°F (111°C). The method of [1], including heating at a β annealing temperature.
[11] The method of [1], wherein β-annealing the workpiece comprises heating the workpiece at a β-annealing temperature for a time in the range of 5 minutes to 24 hours.
[12] The method of [1], further comprising plastically deforming the workpiece in the β phase region of the titanium alloy at a plastic deformation temperature before cooling the β-annealed workpiece.
[13] Plastically deforming the workpiece at the plastic deformation temperature in the β phase region of the titanium alloy includes stretching the workpiece, upsetting, and multiaxially forging at a high strain rate. The method of [12], comprising at least one of:
[14] The method of [12], wherein the plastic deformation temperature is within a range of the β-transus temperature of the titanium alloy to a temperature higher than the β-transus temperature of the titanium alloy by a maximum of 300°F (111°C).
[15] Plastically deforming the workpiece includes multi-axial forging at a high strain rate, and cooling the workpiece includes forging the workpiece in the α+β phase region of the titanium alloy. The method of [12], comprising multi-axially forging the workpiece at a high strain rate when cooling to temperature.
[16] The method of [12], wherein plastically deforming the workpiece includes upsetting forging the workpiece to a β upsetting strain within a range of 0.1 to 0.5.
[17] The workpiece forging temperature is 100°F (55.6°C) below the β transus temperature of the titanium alloy to 700°F (388.9°C) below the β transus temperature of the titanium alloy. The method of [1], which is within the temperature range.
[18] Cooling the adiabatically heated interior region of the workpiece to a temperature at or near the workpiece forging temperature within the workpiece forging temperature range during successive multiple press forgings. The method of [1], further comprising: an intermediate continuous press forging step of heating the outer surface of the workpiece to a temperature at or near the workpiece forging temperature within the workpiece forging temperature range.
[19] The method of [18], wherein the adiabatically heated interior region of the workpiece is cooled for an interior region cooling time in the range of 5 seconds to 120 seconds.
[20] The method of [18], wherein heating the outer surface of the workpiece comprises heating with one or more of flame heating, box furnace heating, induction heating, and radiant heating. ..
[21] The die of the forging furnace used for press forging the workpiece has a temperature within the range of the workpiece forging temperature to a temperature 100°F (55.6°C) below the workpiece forging temperature. The method of [18], which is heated.
[22] The method of [1], wherein after the total strain of at least 1.0 is achieved, the workpiece has an average α-particle size in the range of 4 μm or less.
[23] Repeating at least one of the press forging steps press-forges the workpiece at a second workpiece forging temperature until a total strain of at least 1.0 is achieved in the workpiece. Including the second workpiece forging temperature is in the α-β phase region of the titanium alloy of the workpiece, the second workpiece forging temperature is lower than the workpiece forging temperature, Method [1].
[24] A method for reducing the particle size of a work piece containing a titanium alloy,
Β-annealing the workpiece,
Cooling the β-annealed workpiece to a temperature below the β-transus temperature of the titanium alloy;
Including multi-axis forging the workpiece, the multi-axis forging,
A workpiece forging temperature within the workpiece forging temperature range in the direction of the first orthogonal A-axis of the workpiece at a strain rate sufficient to adiabatically heat the workpiece in the interior region of the workpiece. Press forging to the height of the main reduction spacer with
Press forging the workpiece in the direction of the second orthogonal B-axis of the workpiece at the workpiece forging temperature to a first roughing blank spacer height;
Press forging the workpiece in a direction of a third orthogonal C-axis of the workpiece at a workpiece forging temperature to a second roughing reduction spacer height;
The primary reduction spacer at the workpiece forging temperature at a strain rate sufficient to adiabatically heat the interior region of the workpiece, in the direction of the second orthogonal B-axis of the workpiece. Press forging to height,
Press forging the workpiece in the direction of the third orthogonal C-axis of the workpiece at the workpiece forging temperature to the first roughing reduction spacer height;
Press forging the workpiece in the direction of the first orthogonal A-axis of the workpiece at the workpiece forging temperature to the second roughing reduction spacer height;
The primary reduction spacer at the workpiece forging temperature at a strain rate sufficient to adiabatically heat the interior region of the workpiece in the direction of the third orthogonal C-axis of the workpiece. Press forging to height,
Press forging the workpiece in the direction of the first orthogonal A axis of the workpiece at the workpiece forging temperature to the first roughing reduction spacer height;
Press forging the workpiece in the direction of the second orthogonal B axis of the workpiece at the workpiece forging temperature to the second roughing reduction spacer height;
Repeating at least one of the preceding press forging steps until a total strain of at least 1.0 is achieved in the workpiece.
[25] The method of [24], wherein at least one of the press forging steps is repeated until a total strain of at least 1.0 up to less than 3.5 is achieved in the workpiece.
[26] The method of [24], wherein the strain rate used during press forging is in the range of 0.2 sec ^{−1 to} 0.8 sec ⁻¹ .
[27] The method of [24], wherein the workpiece comprises one of an α+β titanium alloy and a metastable β titanium alloy.
[28] The method of [24], wherein the workpiece includes an α+β titanium alloy.
[29] The method of [27] or [28], wherein the titanium alloy comprises at least one of a grain pinning alloying additive and a β-stabilizing content that reduces α-phase precipitation and α-phase growth rate.
[30] The workpiece is made of Ti-6Al-2Sn-4Zr-6Mo alloy (UNS R56260), Ti-6Al-2Sn-4Zr-2Mo-0.08Si alloy (UNS R54620), Ti-4Al-2.5V alloy. The method of [24], including a titanium alloy selected from (UNS R54250), Ti-6Al-7Nb alloy (UNS R56700), and Ti-6Al-6V-2Sn alloy (UNS R56620).
[31] The method of [24], wherein cooling the β-annealed workpiece comprises cooling the workpiece to ambient temperature.
[32] The method of [24], wherein cooling the β-annealed workpiece includes cooling the workpiece to the workpiece forging temperature.
[33] β-annealing the workpiece may be performed within a temperature range of the workpiece from the β-transus temperature of the titanium alloy to the β-transus temperature of the titanium alloy at a maximum of 300°F (111°C). The method of [24], which comprises heating at a β annealing temperature.
[34] The method of [24], wherein β-annealing the workpiece comprises heating the workpiece at a β-annealing temperature for a time in the range of 5 minutes to 24 hours.
[35] Before the β-annealed workpiece is cooled to a temperature below the β-transus temperature of the titanium alloy, the workpiece is plastically deformed at a plastic deformation temperature in a β-phase region of the titanium alloy. The method of [24], further comprising:
[36] Plastically deforming the workpiece at the plastic deformation temperature in the β phase region of the titanium alloy includes stretching, upsetting forging, and multiaxially forging at a high strain rate. The method of [35], comprising at least one of the following:
[37] The plastic deformation temperature is within a range of the β-transus temperature of the titanium alloy of the workpiece to a temperature 300°F (111°C) higher than the β-transus temperature of the titanium alloy of the workpiece. , [35] method.
[38] Plastically deforming the workpiece includes multi-axial forging at a high strain rate, and cooling the β-annealed workpiece means that the workpiece is the α+β phase of the titanium alloy. The method of [35], comprising multi-axially forging the workpiece at a high strain rate as it cools to the workpiece forging temperature in the region.
[39] The method of [35], wherein plastically deforming the workpiece includes upsetting forging the workpiece to a β upsetting strain within a range of 0.1 to 0.5.
[40] The workpiece forging temperature is in a range of 100°F (55.6°C) below the β transus temperature of the titanium alloy to 700°F (388C) below the β transus temperature of the titanium alloy. The method of [24].
[41] During successive press forging, the adiabatically heated interior region of the workpiece is cooled to a temperature at or near the workpiece forging temperature within the workpiece forging temperature range. The method of [24], wherein the outer surface region of the workpiece is heated to a temperature at or near the workpiece forging temperature within the workpiece forging temperature.
[42] The method of [41], wherein the adiabatically heated interior region of the workpiece is cooled for a time in the range of 5 seconds to 120 seconds.
[43] The method of [41], wherein heating the outer surface of the workpiece includes heating with one or more of flame heating, box furnace heating, induction heating, and radiant heating. ..
[44] The die of the forging furnace used for press forging the workpiece has a temperature within a range of the workpiece forging temperature to a temperature 100°F (55.6°C) below the workpiece forging temperature. The method of [41], wherein the method is heated.
[45] The method of [24], wherein the workpiece has an average alpha particle size of 4 μm or less after a total strain of at least 1.0 has been achieved.
[46] repeating at least one of the press forging steps press-forges the workpiece at a second workpiece forging temperature until a total strain of at least 1.0 is achieved in the workpiece. Wherein the second workpiece forging temperature is within the α-β phase region of the titanium alloy workpiece, the second workpiece forging temperature is lower than the workpiece forging temperature, [24 ]the method of.

Claims (52)

A method of processing a workpiece made of titanium or titanium alloy, comprising:
Β-annealing the workpiece,
Cooling the β-annealed workpiece to a temperature below the β-transus temperature of the titanium alloy, and forging the workpiece along a plurality of axes, the workpiece along a plurality of axes. Forging a piece includes:
Press forging the workpiece at a strain rate that adiabatically heats an internal region of the workpiece, along a first axis of the workpiece, within a forging temperature range,
Press forging the workpiece at a strain rate that adiabatically heats the interior region of the workpiece, along a second axis of the workpiece, within the forging temperature range,
Press forging the workpiece within the forging temperature range, along a third axis of the workpiece at a strain rate that adiabatically heats the interior region of the workpiece,
Wherein the first axis, the second axis, and the third axis are not the same or parallel, and
Repeating at least one of the press forging,
The method wherein the forging of the workpiece along a plurality of axes results in a total true strain in the workpiece of at least 1.0 and less than 3.5. The method of claim 1, wherein the strain rate used in forging the workpiece along multiple axes is in the range of 0.2 sec ^{-1 to} 0.8 sec ^-1 . The method of claim 1, wherein the workpiece comprises one of an α+β titanium alloy and a metastable β titanium alloy. The method of claim 1, wherein the workpiece comprises an α+β titanium alloy. The method of claim 3 or 4, wherein the titanium alloy comprises at least one of a grain pinning alloying additive and a β-stabilizing content effective to reduce α-phase precipitation and growth rate. The method of claim 1, wherein the workpiece comprises a titanium alloy selected from UNS R56260, UNS R54620, UNS R54250, UNS R56700, and UNS R56620. The method of claim 1, wherein cooling the β-annealed workpiece comprises cooling the workpiece to room temperature. The method of claim 1, wherein cooling the β-annealed workpiece comprises cooling the workpiece to a temperature at or near the workpiece forging temperature. Β-annealing the workpiece comprises heating the workpiece at a β-annealing temperature within a range of up to 166.7° C. above the β-transus temperature of the titanium alloy to the β-transus temperature of the titanium alloy. The method of claim 1, comprising: The method of claim 1, wherein beta annealing the workpiece comprises heating the workpiece for a time in the range of 5 minutes to 24 hours. The method of claim 1 further comprising plastically deforming the workpiece at a temperature within the β phase region of the titanium alloy prior to cooling the β-annealed workpiece. The method of claim 11, wherein plastically deforming the workpiece comprises at least one of stretching, upsetting, and multi-axially forging at a high strain rate. Plastic deforming the workpiece comprises deforming the workpiece at a temperature within the range of up to 166.7° C. above the β transus temperature of the titanium alloy to the β transus temperature of the titanium alloy. Item 11. The method according to Item 11. Plastically deforming the workpiece includes multiaxially forging the workpiece at a high strain rate, and cooling the workpiece causes the workpiece to a temperature within the α+β phase region of the titanium alloy. The method of claim 11, comprising multi-axially forging the workpiece at a high strain rate as it cools. The method of claim 11, wherein plastically deforming the workpiece comprises upset forging the workpiece to a strain in the range of 0.1 to 0.5. The press forging is performed while the workpiece is at a temperature in the range of 55.6° C. below the β transus temperature of the titanium alloy to 388.9° C. below the β transus temperature of the titanium alloy. The method of claim 1, wherein 2. The method of claim 1, further comprising cooling the adiabatically heated interior region of the workpiece between successive press forgings to a temperature at which the next press forging is performed. Method. During successive press forgings, the adiabatically heated interior region of the workpiece cools for a time in the range of 5 seconds to 120 seconds before the next press forging is performed. 18. The method of claim 17, wherein the method is performed. 18. The forging furnace die used to press forge the workpiece is heated to a temperature that is 55.6[deg.]C or more below the temperature of the workpiece on which the workpiece is press forged. Method. The method of claim 1, wherein the workpiece comprises an average alpha particle size in the range of 4 μm or less after a total true strain of at least 1.0 has been achieved. The method of claim 1, wherein the titanium alloy is UNS R54620 and the forging temperature range is 604.4°C to 826.7°C . The method of claim 1, wherein the titanium alloy is UNS R56260 and the forging temperature range is 548.9°C to 882.2°C. The method of claim 1, wherein the titanium alloy is UNS R54250 and the forging temperature range is 582.2°C to 915.6°C. The method of claim 1, wherein the titanium alloy is UNS R56620 and the forging temperature range is 527.2°C to 890.6°C. The method of claim 1, wherein in each press forging, the strain rate of the forging adiabatically heats the interior region of the workpiece by 55.6°C to 166.7°C. The titanium alloy is UNS R54620,
The forging temperature range is 604.4°C to 826.7°C, and each press forging is at a strain rate that adiabatically heats the internal region of the workpiece by 55.6°C to 166.7°C. is there,
The method of claim 1. During successive press forgings, the adiabatically heated interior region of the workpiece cools for a time in the range of 5 seconds to 120 seconds before the next press forging is performed. 27. The method of claim 26, which is performed. The titanium alloy is UNS R56260,
The forging temperature range is 548.9°C to 882.2°C, and each press forging is at a strain rate that adiabatically heats the interior region of the workpiece by 55.6°C to 166.7°C. is there,
The method of claim 1. During successive press forgings, the adiabatically heated interior region of the workpiece cools for a time in the range of 5 seconds to 120 seconds before the next press forging is performed. 29. The method of claim 28, wherein the method is performed. The titanium alloy is UNS R54250,
The forging temperature range is 582.2°C to 915.6°C, and each press forging is at a strain rate that adiabatically heats the interior region of the workpiece by 55.6°C to 166.7°C. is there,
The method of claim 1. During successive press forgings, the adiabatically heated interior region of the workpiece cools for a time in the range of 5 seconds to 120 seconds before the next press forging is performed. 31. The method of claim 30, wherein the method is performed. The titanium alloy is UNS R56620,
The forging temperature range is 527.2°C to 890.6°C, and each press forging is at a strain rate that adiabatically heats the internal region of the workpiece by 55.6°C to 166.7°C. is there,
The method of claim 1. During successive press forgings, the adiabatically heated interior region of the workpiece cools for a time in the range of 5 seconds to 120 seconds before the next press forging is performed. 33. The method of claim 32, which is performed. A method for reducing the particle size of a work piece made of titanium or a titanium alloy,
Heating the workpiece with a starting cross-sectional dimension to a workpiece forging temperature within a workpiece forging temperature range within the α+β phase region of the metallic material;
Upset forging the workpiece within the workpiece forging temperature range, and multi-pass stretch forging the workpiece within the workpiece forging temperature range, including:
Multi-pass stretch forging includes incrementally rotating the entire workpiece in a direction of rotation, and then stretch forging the workpiece after each incremental rotation,
Incremental turning and stretch forging are repeated until a true strain of at least 3.5 is achieved in the workpiece, and
The method wherein the workpiece is not heated during the multi-pass draw forging. The method of claim 34, wherein the strain rates used in upset forging and stretch forging are in the range of 0.001 sec ^{-1 to} 0.02 sec ^-1 . The work piece comprises a cylindrical work piece and incrementally rotating and draw forging rotate the entire cylindrical work piece in 15 degree increments until the cylindrical work piece is rotated by 360 degrees. 35. The method of claim 34, further comprising: and then draw forging after each rotation. The work piece comprises a regular octagonal work piece, and incrementally rotating and draw-forging includes rotating the entire regular octagonal work piece in 45 degree increments until the regular octagonal work piece is rotated 360 degrees. 35. The method of claim 34, further comprising rotating and then draw forging after each rotation. 35. The method of claim 34, wherein the workpiece comprises a titanium alloy selected from the group consisting of alpha titanium alloys, alpha+beta titanium alloys, metastable beta titanium alloys, and beta titanium alloys. The method of claim 34, wherein the workpiece comprises an α+β titanium alloy. 35. The work piece of claim 34, wherein the work piece comprises one of ASTM grades 5, 6, 12, 19, 20, 21, 23, 24, 25, 29, 32, 35, 36, and 38 titanium alloys. the method of. heating the workpiece to a β soaking temperature,
Holding the workpiece at the β soak temperature for a β soak time sufficient to form a 100% β phase microstructure in the workpiece, and in the α+β phase region of the metallic material. 35. The method of claim 34, further comprising cooling the workpiece to room temperature prior to heating the workpiece to the workpiece forging temperature within the workpiece forging temperature range. 42. The method according to claim 41, wherein the β soaking temperature is in a temperature range of a β transus temperature of the metal material to a temperature which is a maximum of 166.7° C. higher than the β transus temperature of the metal material. The method according to claim 41, wherein the β soaking time is 5 minutes to 24 hours. 42. The method of claim 41, further comprising plastically deforming the workpiece at a plastic deformation temperature within the beta phase region of the metallic material prior to cooling the workpiece to room temperature. Plastically deforming the workpiece includes at least one of stretching the workpiece, upsetting, and multiaxially forging at a high strain rate, wherein the workpiece has a high strain rate. 45. The method of claim 44, wherein the multi-axial forging comprises multi-axial forging at a strain rate of 0.2 sec ^{-1 to} 0.8 sec ^-1 . The method according to claim 44, wherein the plastic deformation temperature is within a plastic deformation temperature range of the β-transus temperature of the metal material to a temperature that is 166.7° C. higher than the β-transus temperature of the metal material at maximum. 47. The plastic deformation of the workpiece comprises multiple upsetting and draw forging, and cooling the workpiece to room temperature comprises air cooling the workpiece. Method. 35. The method of claim 34, wherein the workpiece forging temperature range is 55.6[deg.]C below the [beta] Transus temperature of the metallic material to 388.9[deg.]C below the [beta] Transus temperature of the metallic material. 35. The method of claim 34, further comprising repeating the heating, upset forging, and multi-pass draw forging until a true strain of at least 10 is achieved in the workpiece. 50. The method of claim 49, upon completion of the method, the microstructure of the metallic material comprises ultrafine sized α particles having an α particle size of 4 μm or less. Following multi-pass stretch forging of the workpiece within the workpiece forging temperature range,
Cooling the workpiece to a temperature within a second workpiece forging temperature range in the α+β phase region of the metallic material,
Upset forging the workpiece within the second workpiece forging temperature range,
Multipass draw forging the workpiece within the second workpiece forging temperature range,
Here, multi-pass stretch forging includes incrementally rotating the entire workpiece in a direction of rotation, and then stretch forging the titanium alloy workpiece after each revolution, and
Incrementally rotating and stretch forging are repeated until the workpiece comprises the starting cross-sectional dimension, and the second workpiece forging is performed until a true strain of at least 10 is achieved in the workpiece. 35. The method of claim 34, further comprising repeating the upset forging and the multi-pass draw forging within a temperature range. 52. The method of claim 51, wherein the strain rates used in upset forging and stretch forging are in the range of 0.001 sec- ^{1 to} 0.02 sec- ¹ .