JP2018021253A - LOW COST α-β TITANIUM ALLOY WITH GOOD BALLISTIC AND MECHANICAL PROPERTY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an α-β titanium alloy having improved mechanical and ballistic properties formed using a low-cost composition.SOLUTION: The titanium alloy is provided that has a composition containing, by wt.%, 4.2 to 5.4% of Al, 2.5 to 3.5% of V, 0.5 to 0.7% of Fe, 0.15 to 0.19% of O and the balance Ti. The titanium alloy has a tensile yield strength of at least about 120,000 psi and an ultimate tensile strength of at least about 128,000 psi in both longitudinal and transverse directions, a cross section reduction rate of at least about 43%, and an elongation of at least about 12%, and about a 0.430-inch-thick plate has a Vballistic limit of about 1936 fps. The titanium alloy is produced using a combination of a recycled and/or virgin material, thereby providing low-cost means for forming a high-quality armor plate for use in a military system.SELECTED DRAWING: Figure 1

Description

This application is an international PCT application and is incorporated herein by reference in its entirety.
Has the benefit of priority of US application Ser. No. 12 / 850,691, filed Aug. 5, 0.

The present invention generally relates to titanium (Ti) alloys. In particular, an α-βTi alloy realized with a relatively low cost component and having an improved combination of ballistic and mechanical properties has been described along with a method for producing the titanium alloy.

Ti alloys have found wide application in applications that require high weight specific strength, good corrosion resistance, and retention of these properties at high temperatures. Despite these advantages, the use of high raw material costs and processing costs compared to steel and other alloys is more important than application areas where improved efficiency and properties are more important than relatively high costs. Is strictly limited. Some typical applications that have benefited from incorporating Ti alloys into various capacities include, for example, aircraft components, medical equipment, high performance automobiles, high-end exercise equipment and military applications.

A conventional titanium-based alloy that has been successfully used in military systems is Ti-6Al-4V, known as Ti64. As the name suggests, these Ti alloys are typically typically 0.3.
It contains no more than 0 wt% iron and no more than 0.3 wt% oxygen and contains 6 wt% aluminum and 4 wt% vanadium.

The development of Ti64 has resulted in an alloy with an attractive combination of ballistic and mechanical properties for military land vehicle systems. Military applications where weldable forged titanium alloys such as Ti64 are implemented as structural armor plates typically have strict compositional and performance requirements.
For example, in a document titled MIL-DTL-46077G, 2006, “Detailed Specifications: Armored Plate, Titanium Alloy, Weldable”, the US Department of Defense has a strict elemental composition range with minimal mechanical and ballistic properties. And provisions for four categories of Ti64 forged titanium alloy armor defined by density requirements. Thus, with respect to titanium alloy-based armor plates, the objective is to provide a titanium alloy that meets or exceeds defined standards while minimizing the associated raw materials and processing costs.

Attempts have been made to produce titanium alloys with the required performance combinations at reduced costs. For example, titanium alloys are manufactured by the electron beam single melting method (EBSM). This approach made the production of titanium alloys more cost effective and allowed the introduction of titanium alloys into further military systems. Another approach is to reduce the cost of raw materials in order to reduce raw material costs, as disclosed, for example, by Kosaka et al. (Hereinafter Kosaka) US Pat. No. 6,786,985.
Instead of vanadium (V) as a stabilizing element, we are focusing on replacing it with a fixed amount of iron (Fe). However, the titanium alloy developed by Kosaka required the inclusion of molybdenum (Mo).

Further efforts include, for example, Adams et al. (Adams) US Pat. No. 5,342,
As disclosed in the '458 specification, as a whole, within the temperature range in the β-phase region of the alloy,
He is involved in the development of titanium alloy compositions that can be processed from ingots to final rolled products. Adam
In terms of s, the high ductility and low flow stress present at higher temperatures in the above-described alloys minimizes surface and edge cracking, thereby improving yield. Yoji Kosaka
U.S. Pat.No. 5,980,655 and William W. Love U.S. Pat.No. 5,332,545, in which improved mechanical strength is achieved by increasing the oxygen concentration to a range beyond that defined by military guidelines. And efforts to form titanium alloys having ballistic properties.

Several titanium alloys that have a composition similar to Ti64 but have additional components therein are also known in the art. These titanium alloys were developed specifically to provide low cost, high strength titanium alloys with acceptable levels of ductility. As an example, Pa
U.S. Patent No. 7,008,489 to ul J. Bania discloses a titanium alloy having an improved ductility of at least 20% at certain strength levels in its examples. However, in addition to the basic Ti-Al-V-Fe-O component present in Ti64, the disclosed alloys include tin (Sn), zirconium (
It also contains components of Zr), chromium (Cr), molybdenum (Mo) and silicon (Si). The many elements in these alloys inevitably increase the raw material costs of the titanium alloys formed as described above.

Another example is provided by Nasserraffi et al., US Patent Application Publication No. 2006/0045789, and is directed to titanium alloys made from recycled titanium. In the examples, Nasserraffi discloses a titanium alloy containing Ti-Al-V, but the alloy is also
Contains one or more elements selected from the group consisting of Cr, Fe, and manganese (Mn) at a concentration of 1.0 to 1.5 weight percent. The relatively high levels and low ductility of Cr, Fe, and Mn limit the application of alloys to military systems. Each of the foregoing patents and patent applications is incorporated by reference in their entirety as if described in this specification.

New and improved titanium that continues to achieve the lowest mechanical and ballistic performance standards at a lower cost, despite improvements in terms of composition, properties and processing costs achieved to date There is a continuing need to develop alloys and related manufacturing methods.

Disclosed is a titanium alloy that is achieved using a low cost composition and has a good combination of ballistic and mechanical properties. Such titanium alloys are particularly advantageous for use as armor plates in military applications, but are not limited thereto and are suitable for many other applications. In one embodiment, the titanium alloy consists essentially of 4.2 to 5.4% aluminum, 2.5 to 3.5% vanadium, 0.5 to 0.7% iron, 0.15 to 0.19% oxygen and the balance titanium, by weight percent. Become. In a particular embodiment, the titanium alloy consists essentially of, by weight, about 4.8% aluminum, about 3.0% vanadium, about 0.6% iron, about 0.17% oxygen, and the balance titanium. In yet another embodiment, the maximum concentration of any impurity element present in the titanium alloy is 0.1% by weight, and the combined concentration of all impurities is 0.4% or less.

A titanium alloy having the disclosed composition has a tensile yield strength of at least about 120,000 psi in both the longitudinal and transverse directions and a maximum tensile strength of at least about 128,000 psi with a cross-sectional reduction of at least about 43% And has the advantage of providing a low cost titanium alloy having an elongation of at least about 12%. The titanium alloy, in certain embodiments, can be formed into a plate having a thickness between about 0.425 inches to about 0.450 inches and having a ballistic limit V ₅₀ of at least about 1,848 fps. In a more specific embodiment, the titanium alloy plate is
It has a thickness of about 0.430 inches and a ballistic limit V ₅₀ of about 1936 fps.

In one embodiment, the titanium alloy has a β isomorphic (β _ISO ) to β eutectoid (β _EUT ) stabilizing element ratio (β _{ISO /} β _EUT ) of about 0.9 to about 1.7 and a β eutectoid (β _EUT ) β isomorphism (
The proportion of stabilizing elements in (βISO) is defined as
In the formulas provided throughout this specification, Mo, V, Cr, and Fe represent the weight percentages of molybdenum, vanadium, chromium, and iron, respectively, in the titanium alloy. In certain embodiments, the ratio of β isomorphic (β _ISO ) stabilizing elements to β eutectoid (β _EUT ) is about 1.2.

In another embodiment, the titanium alloy has a molybdenum equivalent weight (Mo _eq ) of about 3.1 to about 4.4, where the molybdenum equivalent is defined as:
In certain embodiments, the molybdenum equivalent is about 3.8. In yet another embodiment, the titanium alloy has an aluminum equivalent of about 8.3 to about 10.5, where the aluminum equivalent is defined as:
Al _eq = Al + 27O
In this formula, Al and O are the weight percentages of aluminum and oxygen in the titanium alloy, respectively.
Indicates. In certain embodiments, the aluminum equivalent is about 9.4.

In another embodiment, the titanium alloy has a beta transformation temperature (Tβ) of about 1732 ° F. to about 1820 ° F.
However, the β transformation temperature of ° F is defined as:
T _β = 1607 + 39.3Al + 330O + 1145C + 1020N-21.8V-32.5F-17.3Mo-70Si-27.3Cr
In this formula, C, N, and Si represent the weight percentages of carbon, nitrogen, and silicon, respectively, in the titanium alloy. In certain embodiments, the beta transformation temperature is about 1775 degrees Fahrenheit. In certain embodiments, the titanium alloy has a density of about 0.161 pounds per cubic inch (lb / in ³ ) to
It is in the range of about 0.163 lb / in ³ , and in certain embodiments is about 0.162 lb / in ³ .

In another embodiment, the titanium alloy production method basically consists of 4.2-5.4% aluminum, 2.5-3.5% vanadium, 0.5-0.7% iron, 0.15-0.19% oxygen and the balance by weight. Of titanium is disclosed. In certain embodiments, in a cold hearth furnace, the titanium alloy melts a composite of recycled and / or genuine materials that includes aluminum, vanadium, iron and titanium in appropriate proportions to form a molten alloy. And the titanium alloy is produced from the step of putting the molten alloy into the mold. Recycled materials may include, for example, Ti64 Dalai powder and commercial pure (CP) titanium scrap. Pure materials may include, for example, titanium sponge, iron powder and aluminum balls. In another specific embodiment, the recycled material is about 70
It contains 4% Ti64 Dalai powder, about 28.0% titanium sponge, about 0.4% iron and about 1.1% aluminum balls.

In another embodiment, the titanium alloy has a rectangular shape and is 4.2 to 5.4% by weight.
Of aluminum, 2.5 to 3.5% vanadium, 0.5 to 0.7% iron, 0.15 to 0.19% oxygen and the balance of titanium are cast into a rectangular mold. In certain embodiments, the input slab is subjected to an initial furnace or rolling process at an abnormal temperature of the β transition temperature and a temperature lower than the β transition temperature before being sintered at a temperature lower than the β transition temperature. The process of final rolling is performed.

The titanium alloys disclosed herein provide an alternative to conventional Ti64 that meets or exceeds the mechanical and ballistic properties specified for Ti64 while being relatively inexpensive. This price reduction will allow the use of titanium alloys in a wider range in various military and other applications requiring similar characteristics.

The accompanying drawings are incorporated into and constitute a part of this disclosure, and illustrate exemplary embodiments of the disclosed invention and serve to explain the nature of the disclosed invention.
FIG. 1 is a flowchart illustrating a method for producing a titanium alloy according to a representative embodiment of the presently disclosed invention. FIG. 2A is a schematic diagram of a 30 caliber M2 bullet of a real armor bullet. FIG. 2B is a photograph of a real caliber 30 caliber M2 bullet used in the actual test. Figure 3 illustrates the arrangement of the sighting field used for testing V ₅₀ ballistic limit of the armor plate. FIG. 4 is an example showing the penetration probability of the armor plate with respect to the firing speed measured at the midpoint between the muzzle and the armor plate. FIG. 5 is a graph showing the V ₅₀ bullet limit for a typical titanium alloy according to the plate thickness. FIG. 6 is an enlarged view of FIG. 5 in the thickness range of 0.40 to 0.46 inches, showing the V ₅₀ bullet limit as a function of plate thickness for a typical titanium alloy.

Throughout the drawings, the same reference numerals and letters are used to designate like features, elements, parts or portions of the illustrated embodiments unless otherwise stated. The disclosed invention will now be described in detail with reference to the figures but relates to the illustrated embodiments.

A representative titanium alloy formed using relatively low cost materials and having favorable mechanical and ballistic properties is described. These titanium alloys are especially for use as armor plates in military systems or for applications where metal alloys with good strength per unit weight and good resistance to bullet penetration in impact are required. Is suitable. The disclosed titanium alloys achieve a combination of mechanical and ballistic properties that meet minimum military standards while reducing compositional and processing costs. Lower raw materials and processing costs are
For more favorable cost considerations, it will facilitate wider adoption of the disclosed titanium alloys.

In one embodiment, a representative titanium alloy comprises, by weight percentage, 4.2-5.4% aluminum, 2.5-3.5% vanadium, 0.5-0.7% iron, 0.15-0.19% oxygen,
It has the balance of titanium and incidental impurities.

Aluminum as an alloying element in titanium increases the temperature at which the α phase becomes stable,
α-stabilizing element. In one embodiment, the aluminum is in a titanium alloy,
Present in 4.2 to 5.4% weight percent. In certain embodiments, the aluminum is about 4.8 w.
t% exists.

Vanadium, an alloying element in titanium, is an isomorphic β-stabilizing element that lowers the β transition temperature. In one embodiment, vanadium is present in the titanium alloy at a weight percent of 2.5-3.5%. In certain embodiments, vanadium is present at about 3.0 wt%.

Iron as an alloying element in titanium is a eutectoid β-stabilizing element that lowers the β transition temperature, and iron is a strengthening element at ambient temperature. In one embodiment, iron is present in the titanium alloy at 0.5 to 0.7% by weight. In certain embodiments, iron is present at about 0.6 wt%. However, if the iron concentration exceeds the upper limit disclosed in this specification, there is a risk of excessive solute segregation during ingot solidification, which adversely affects ballistic and mechanical properties. on the other hand,
Using sub-limit levels of iron disclosed in this specification will produce alloys that do not achieve the desired strength and ballistic properties.

Oxygen as an alloying element in titanium is an alpha stabilizing element, and iron is an effective strengthening element for titanium alloys at ambient temperatures. In one embodiment, oxygen is in the titanium alloy,
Present at 0.15 to 0.19% by weight. In certain embodiments, oxygen is present at about 0.17 wt%. If the oxygen content is too small, the strength is too low, the β transition temperature is too low, and the cost of the titanium alloy may increase. This is because the waste metal is not suitable for use in dissolving the titanium alloy. On the other hand, if the oxygen content is too large, the resistance to cracking after ballistic impact may be degraded.

According to some embodiments of the invention, the titanium alloy is inevitable impurities at a concentration corresponding to the impurity level, or Mo, Cr, N, C, Nb, Sn, Zr, Ni, Co, Cu, Other components such as Si can also be included. Nitrogen (N) may also be present at concentrations up to 0.05 wt%. In certain embodiments, the maximum concentration of any impurity element is 0.1 wt%, and the combined concentration of all impurities does not exceed a total of 0.4 wt%.

According to one embodiment, the titanium alloy has a β isomorphic (βISO) stabilizing element ratio (β _ISO / β _EUT ) to β eutectoid (β _EUT ) of about 0.9 to about 1.7, The ratio of the β isomorphous stabilizing element to the analysis is defined by equation (1) as follows.
In the mathematical formulas provided throughout this specification, Mo, V, Cr and Fe represent the weight percentages of molybdenum, vanadium and iron in the titanium alloy, respectively. In certain embodiments, the ratio of β isomorphic stabilizing element to β eutectoid is about 1.2.

According to another embodiment, the titanium alloy has a molybdenum equivalent weight (Moeq) of about 3.1 to about 4.4, wherein the molybdenum equivalent is defined by formula (2) as follows:
In certain embodiments, the molybdenum equivalent is about 3.8. Mo and Cr are not the main constituents of the disclosed titanium alloys, but they may be present in small concentrations (eg at or below the level of impurities) (β _ISO / β _EUT ) And can be used to calculate Mo _eq . In another embodiment, the titanium alloy has an aluminum equivalent (Al _eq ) of about 8.3 to about 10.5, where the aluminum equivalent is defined by equation (3) as follows:
Al _eq = Al + 27O (3)
In this formula, Al and O represent the weight percentages of aluminum and oxygen in the titanium alloy, respectively. In certain embodiments, the aluminum equivalent is about 9.4.

In another embodiment, the titanium alloy has a β transformation temperature (T _β ) of about 1732 to about 1820 ° F., and the β transformation temperature at ° F is expressed by the following formula (4): Defined by
T _β = 1607 + 39.3Al + 330O + 1145C + 1020N-21.8V-32.5Fe-17.3Mo-70Si-27.3Cr. (4)
In this formula, C, N, and Si represent the weight percentages of carbon, nitrogen, and silicon in the titanium alloy, respectively. As is the case with molybdenum equivalents, C, N and Si are not major constituents, but they may be present as incidental impurities. In certain embodiments, the β transition temperature is about 1775 ° F.

The titanium alloy has, for example, a tensile yield strength (TY in both the length direction and the transverse direction).
S) is at least 120,000 pounds per square inch (psi) and has excellent tensile properties with a maximum tensile strength of at least about 128,000 psi. In another embodiment, the titanium alloy has an elongation of at least about 12% and / or has a cross-sectional reduction of about 43%. Titanium alloy density is about 0.161 pounds per cubic inch (lb / in ³ )
It is calculated to be between about 0.163lb / in ³ of a nominal density of about 0.162lb / in ^3.

The titanium alloy further provides excellent ballistic properties. The measurement of the effect of the ballistic version is given by the average speed (V ₅₀ ) of the shell or bullet required to penetrate the plate. For example, about 0.425
And a titanium alloy having a ballistic limit V ₅₀ of at least about 1848 fps. In certain embodiments, a plate titanium alloy about 0.430 inches thick has a V ₅₀ ballistic limit of about 1936 fps. Procedure used to measure the V ₅₀ ballistic limit of the titanium alloy is described in connection with the examples provided below.

In another embodiment, a plate comprising the titanium alloy described in this disclosure is provided. In certain embodiments, the titanium alloys shown here are used as armor plates. However, other suitable uses for titanium alloys include, but are not limited to, military systems and other components in automotive and aircraft parts such as seat trucks and erosion protection shields.

In yet another embodiment, a method for producing a titanium alloy having good mechanical and ballistic properties is disclosed. The method is basically 4.2 to 5.4, in weight percent.
% Of aluminum, 2.5-3.5% vanadium, 0.5-0.7% iron and 0.15-0.19% oxygen with the balance titanium to produce a titanium alloy with the appropriate proportion of raw material composite include. Melting can be performed, for example, in a cold hearth furnace. In certain embodiments, the raw material combines a small amount of iron and aluminum and includes a composite of recycled and pure materials such as titanium waste and titanium sponge. Under most market conditions, the use of recycled materials offers significant cost savings. Recycled materials used can include, but are not limited to, Ti64, Ti-10V-2Fe-3Al, other Ti-Al-V-Fe alloys, and CP titanium. The recycled material may be in the form of machined shavings (Dalai powder), solid pieces, or re-dissolved electrodes. The pure material used can include, but is not limited to, titanium sponge, aluminum-vanadium master alloy, iron powder or aluminum bullet.
Since an aluminum-vanadium master alloy is not essential, significant cost savings are achieved.
However, this does not preclude the use and addition of unused raw materials containing titanium sponge and alloying elements rather than recycled materials when required.

In some embodiments, the production method includes the step of performing annealing heat treatment of titanium at a transition temperature (eg, a β transformation temperature or lower). The titanium alloy used can have any of the properties described in this specification.

In some embodiments, the production method also includes a vacuum arc remelting (VAR) step of the alloy, and a forging and / or rolling of the titanium alloy above the β transformation temperature, followed by β Forging and / or rolling below the transformation temperature. In certain embodiments, the method of producing a titanium alloy is used for producing parts for military systems, more specifically for producing armor plates.

A flow diagram illustrating an exemplary method of producing a titanium alloy is provided in FIG. Initially, a desired amount of raw material having the appropriate concentration and characteristics is prepared in step 100. In certain embodiments, the raw materials may be combined with pure raw materials of any composition and suitable composition, but include recycled materials. After being prepared, the raw materials are melted and cast in step 110 to make an ingot. Melting can be performed, for example, by VAR, plasma arc melting, electron beam melting, consumable electrode skull melting, or a combination thereof. In a particular embodiment, two melted molds are prepared by the VAR and poured directly into a mold having a cylindrical shape.

In step 120, the ingot undergoes initial forging and rolling. Initial forging and rolling are performed at the β transformation temperature or higher, and rolling is performed in the length direction. Step 130
Ingots undergo final casting and rolling. Final casting and rolling are performed below the β transformation temperature, and rolling is performed in the length direction and the transverse direction. The ingot is then annealed in step 140, and in a particular embodiment is performed at a subtransus temperature. The final rolled product has a thickness ranging from, but not limited to, about 0.1 inches to about 4.1 inches.

In some embodiments, rolling to a gauge of 0.4 inches or less to produce coils or elongated products may be accomplished by hot rolling and optionally cold rolling. However, in another embodiment, rolling to a thin plate product is accomplished by hot or bass rolling of the plate as a single plate or composite plate protected with a steel wrap.

In the examples that follow, further details on representative titanium alloys and production methods are described.

The examples provided in this section are useful in explaining the manufacturing process used, resulting in the composition and subsequent properties of titanium alloys prepared according to the examples of the present invention. The titanium alloys and associated production methods described below are provided by way of illustration and are not intended to be limiting.

(Comparative example)
Several titanium alloys having element concentrations outside the V, Fe and O ranges disclosed in this specification were first prepared for serving as comparative examples. Comparative titanium alloys were made by mixing with the raw materials to achieve the appropriate ratio for each comparative titanium alloy. Titanium alloy # C1 of the comparative example is about 5.0 wt.% Aluminum, about 4.0 wt.% Vanadium,
A nominal composition of about 0.03 wt.% Iron, about 0.22 wt.% Oxygen and the balance titanium was prepared. Comparative titanium alloy # 2 has a nominal composition of about 5.0 wt.% Aluminum, about 4.0 wt.% Vanadium, about 0.03 wt.% Iron, about 0.12 wt.% Oxygen and the balance titanium. Got ready. Titanium alloy # C3 of the comparative example is about 5.0 wt.% Aluminum, about 5.0 wt.% Vanadium, about 0.6 wt.% Iron, about 0.19 w.
Prepared with nominal composition of t.% oxygen and balance titanium.

Titanium alloys # C1-C3 of comparative examples were cast on each ingot having a spherical shape and changed from exceeding the β transition temperature to an intermediate slab. Final rolling and cross rolling were performed at a β transition temperature or lower. The final annealing was performed at a temperature not higher than the β transition temperature. Titanium alloy # C1-C3 of the comparative example has 14
A final anneal was performed at a temperature of 00 ° F. and the sample was cooled in air.

Chemical analysis was performed on the comparative titanium alloy # C1-C3, and mechanical and ballistic characteristics were measured. The measured composition and the calculated Al _eq , Mo _eq , T _β and density are summarized in Table 1 below.

The mechanical properties of the plate containing the titanium alloy # C1-C3 of the comparative example were measured and summarized in Table 2. A large number of measurement results are obtained from one ingot, and the results are provided in the rows separated in the same group range in Table 2. The tensile properties of the plate were measured in both the transverse direction (T) and the length direction (L). In Table 2, ksi represents kilopounds per square inch (1 ksi =
1,000psi). The tensile properties measured in Table 2 are the average values of UTS, TYS, RA and elongation, and for the comparative titanium alloy # C1, 131 ksi, 122.3 ksi, 36% and 10.3%, respectively, the comparative titanium alloy # For C2, 131 ksi, 123 ksi, 34% and 11%, respectively, comparative titanium alloy #C
3 yields 133.8 ksi, 124.3 ksi, 42% and 12.3%, respectively.

The V ₅₀ ballistic limit of the titanium alloy plate of the comparative example, which is the minimum defense, is 0.30 caliber (7.62 mm) 166
Measurements were made using particle armor ammunition (AP) M2 ammunition. A schematic diagram of a cross section of a 0.30 aperture AP M2 circle is provided in FIG. 2A, while a sample is shown in FIG. 2B. The 0.30 caliber ammunition includes a hardened steel core, a tip filler, and a gold plated metal coating. The ballistic test itself is
For example, in “Military Standard: Ballistic Test for V ₅₀ Armor“ MLL-STD-662E, 2006 ””, it was performed according to the standard military test procedure disclosed by the US Department of Defense.

A schematic of the test firing range used for the armor plate V ₅₀ ballistic limit test is shown in FIG.
The first and second optoelectronic screens were used in conjunction with a chronograph to calculate the velocity of the bullets between the weapon muzzle and the target. The test was conducted under environmental conditions (70-75 ° F (21
At −24 ° C.) and 35-75% relative humidity) at a tilt angle of zero degrees. The reported thickness value of each plate is the average thickness measured at each corner of the plate. 0.020 inch thick (0.51mm) 202
A plate that proves 4-T3 aluminum was placed 6 inches (152 mm) behind the target plate. The penetration of the evidence plate was defined as the complete penetration of the armor test sample.

Each test consists of projecting bullets at various velocities and then assessing whether a particular impact was completely penetrated (ie, proof plate perforations) or partial penetration. Then, the average speed of the fastest portion through the slowest complete penetration is used to evaluate the values for V _50. Illustrative calculation results are provided in FIG. 4, which illustrates the probability of penetration (%) as a function of impact velocity (ft / sec or fps) for a 0.430 inch thick titanium alloy plate. . The production method, composition and properties of the titanium alloys tested in FIG.
1 is provided. The black solid rhombus in FIG. 4 represents one shot of a (PP) bullet partially penetrating the plate, and the black solid square represents a (CP) penetrating completely through the plate. The value for V ₅₀ is calculated by averaging the impact velocity resulting in CP with the velocity yielding no PP. The example in FIG. 4 provides a value of V ₅₀ = 1936 fps. As such, the V ₅₀ value is a convenient number to generate and is widely used to quantify the ballistic defense provided by a given armor type for a given threat.

The comparative titanium alloy is about 0.440 inches for the comparative titanium alloy # C1, about 0.449 inches for the comparative titanium alloy # C2, and about 0.426 inches for the comparative titanium alloy # C3. Processed to form a board with inch thickness. The ballistic properties of each of the comparative titanium alloys # C1-C3 were measured according to US Department of Defense standards defined above in connection with FIGS. 2-4, and the results are summarized in Table 3 below. ing. V ₅₀ ballistic limits for titanium alloy # C1-C3 were measured to be about 1922 fps, about 1950 fps, and about 1888 fps, respectively.

Ballistic data calculated for Ti64 having the same thickness as the experimental values obtained for the comparative titanium alloys # C1-C3 are also provided in Table 3. Beyond the calculated V ₅₀ value for Ti64, the V ₅₀ improvement obtained with each comparative titanium alloy is labeled as “Δ vs. Ti64” and is shown in the right hand column of Table 3. included. The V ₅₀ value for titanium alloy # C1-C3 is
The calculated values for Ti64 plates of the same thickness are exceeded by differences of 10, 12 and 16 fps, respectively. The minimum V ₅₀ provided in Table 3 represents the minimum V ₅₀ required by the US Department of Defense in MIL-DTL-46077G, 2006 for a particular thickness. For example, the thickness of 0.440 inches is 18
Requires a minimum V _{50 of} 95 fps. Table 3 have been △ V ₅₀ provided represent the minimum V ₅₀ the difference between V ₅₀ measured for the titanium alloy of the comparative example.

(Example # 1)
A representative titanium alloy defined as titanium alloy # 1 having a nominal composition of about 5.0 wt% aluminum, about 3.0 wt% vanadium, about 0.6 wt% iron, about 0.19 wt% oxygen and the balance titanium, Prepared by first mixing with raw materials to achieve the correct ratio. The cost analysis of the above composition revealed that the finished slab has a significantly lower cost per pound than a regular Ti64 alloy prepared by electron beam single melting.
The raw materials were prepared by VAR into a 6.5 inch diameter double melted ingot.

Titanium alloy # 1 is processed by the same method as titanium alloy # C1-C3 of the comparative example. Titanium alloy # 1 was cast into an ingot and changed from exceeding the β transition temperature to an intermediate slab. after that,
Final rolling and cross rolling are performed below the β transition temperature. Final annealing is performed at a temperature not higher than the β transition temperature. In this example, the final anneal was performed at 1400 ° F. for 2 hours and the sample was allowed to cool in the atmosphere.

Chemical analysis was performed on the resulting titanium alloy # 1 to measure mechanical properties. Titanium alloy # 1 was found to have a composition of 4.82 wt% aluminum, 2.92 wt% vanadium, 0.61 wt% iron, 0.19% oxygen and the balance titanium. Nitrogen was also found to be present at a composition of 0.001 wt%. Titanium alloy plate is also, beta isomorphous against beta eutectoid (β _EUT) (β _ISO
) Stabilizing Element Ratio (β _ISO / β _EUT ) is 1.2, Aluminum _Equivalent Al _eq is 10.0, Molybdenum _Equivalent Mo _eq is 3.7, β Transition Temperature T _β is 1786 ° F, Density 0.162lb / in ³
Met. The tensile properties of the plates were measured with a number of measurements performed on the same sample in both the transverse and longitudinal directions. These measurement results are provided in Table 4 below. The tensile properties measured in Table 4 are 129 ksi average UTS, 121 ksi average TYS,
It has an average RA of 47.5% and an average growth of 13%.

A typical titanium alloy with a composition of 4.82 wt% aluminum, 2.92 wt% vanadium, 0.61 wt% iron, 0.19% oxygen and the balance titanium is processed to yield a plate having a thickness of 0.430 inches. It was. The V ₅₀ value for titanium alloy # 1 was measured to be about 1936 fps. This value exceeds the minimum value of 1864 fps established by the US Department of Defense for armor plates 0.430 inches thick by a ΔV ₅₀ range of 72 fps.

The ballistic data obtained for the comparative titanium alloys # C1-C3 and titanium alloy # 1 are shown in Table 5.
And compared with past results obtained for Ti64 as disclosed. The past results include, for example, “Ballistic evaluation of TIMETAL 6-4 plate for defense against armor-piercing shells”, 9th World Conference on Titanium, Vol. 1172-78, 1999, disclosed by JCFanning, which is incorporated by reference as if fully set forth herein. A strong linear correlation between V ₅₀ and plate thickness for Ti64 alloy was revealed, as shown by the dotted line that is the best match (R ² = 0.9964) to the Ti64 data. An enlarged display of FIG. 5 is provided in FIG. 6 showing the V ₅₀ values obtained for thicknesses ranging from 0.40 to 0.46 inches. Data obtained for a representative titanium alloy # 1 is shown as white triangles in FIGS. 5-6. Titanium alloy # C1-C3 and titanium alloy # 1 of each comparative example showed an increase in V ₅₀ compared to a normal Ti64 alloy of the same thickness, but the results in FIGS. The increase indicates that it was obtained for titanium alloy # 1. That is, the representative titanium alloy # 1 exceeded the Ti64 value with a greater difference than all other alloys. It also exceeded the predicted V ₅₀ value of 1883 fps for Ti64 alloy by 53 fps, a sufficient difference.

And, the typical titanium alloy disclosed in this specification basically includes the balance titanium, and by weight percentage, 4.2-5.4% aluminum, 2.5-3.5% vanadium, 0.5-0.7%.
And low-cost compositions with mechanical and ballistic properties equivalent to or better than ordinary Ti64 alloys. The resulting mechanical and ballistic properties are “military specifications for class 4 armor plates, such as the US Department of Defense specification in MIL-DTL-46077G, 2006,“ Detailed specifications: armor plate, titanium alloy, weldable ”. Is over. The typical titanium alloy disclosed herein has the advantage of providing a lower cost composition and a lower cost means of forming high quality armor plates for use in military systems.

In describing embodiments of the present invention, for purposes of clarity, the following terms will be defined as given below. All tests were conducted in accordance with ASTM E8 regulations, and ballistic tests were conducted in accordance with US Department of Defense test procedures in “Military Standards: V ₅₀ Ballistic Test for Armor”.
Tensile yield strength: the material deviates from the proportional relationship between stress and strain (0.2%)
Engineering tensile stress indicating maximum tensile strength: Calculated from the maximum load during the tensile test conducted until breakage and the original cross-sectional area of the sample, the maximum engineering tensile stress that the material can hold Elastic modulus: Ratio of stress to corresponding strain below the limit of proportionality during tensile test Elongation: Increase in gauge length after failure (expressed as a percentage of the original gauge length) during tensile test
Cross-section reduction rate: reduction in the cross-sectional area of the tensile specimen after fracture during the tensile test (expressed as a percentage of the original cross-sectional area)
V ₅₀ ballistic limit: the average velocity of a particular bullet type required to penetrate an alloy plate having a particular dimension and a point positioned relative to the bullet firing in a specified manner. V ₅₀ is calculated by averaging the impact velocity that causes complete penetration with the impact velocity that causes partial penetration.
α-stabilizing element: an element that causes an increase in β-transformation temperature when dissolved in titanium β-stabilizing element: an element that causes a decrease in β-transformation temperature when dissolved in titanium β-transformation temperature : Minimum temperature at which titanium alloy completes transformation of allotrope from α + β to β crystal structure Eutectoid compound: Intermetallic compound of transition metal formed by decomposition of titanium and titanium-rich β phase Isomorphic β stabilizing element : Β-stabilizing element that has the same phase relationship as β-titanium and does not form an intermetallic compound with titanium, eutectoid β-stabilizing element: β-stabilizing element that can form an intermetallic compound with titanium

It will be appreciated by those skilled in the art that the present invention is not particularly limited to what has been shown and described above. On the contrary, the scope of the present invention is defined by the claims. It should be further understood that the above description is only representative of embodiments. For the convenience of the reader, the above description has focused on representative examples of possible embodiments, examples that teach the principles of the present invention. Other embodiments may result from different combinations of parts of different embodiments.

The description does not attempt to exhaustively enumerate all possible changes. Alternative embodiments may not be provided for certain parts of the invention and may result from different combinations of the parts described. Also, the fact that other undescribed alternative embodiments may be available for certain parts is not considered a waiver of such alternative embodiments. It will be appreciated that many of the embodiments not described are within the literal scope of the claims and others are equivalent. further,
All references, publications, U.S. patents and publications of U.S. patent applications cited throughout this specification are fully described in this specification by reference in their entirety. Built in.

All percentages provided are percentages by weight (wt.%) In both the specification and the claims.

Claims (23)

Basically, by weight, 4.2-5.4% aluminum, 2.5-3.5% vanadium, 0.5-0.7
% Iron. A titanium alloy consisting of 0.15-0.19% oxygen and the balance titanium. The alloy consists essentially of, by weight, about 4.8% aluminum, about 3.0% vanadium, about 0.6% iron, about 0.17% oxygen and the balance titanium. The titanium alloy according to claim 1. The alloy has a ratio of β isomorphic (βISO) stabilizing elements to β eutectoid (βEUT) (βISO / β
EUT) is about 0.9 to about 1.7, and (βISO / βEUT) is defined as:
2. The titanium alloy according to claim 1, wherein Mo, V, Cr, and Fe respectively represent weight percentages of molybdenum, vanadium, chromium, and iron in the alloy. The alloy has a ratio of β isomorphic (βISO) stabilizing elements to β eutectoid (βEUT) (βISO / β
4. The titanium alloy of claim 3, wherein EUT) is about 1.2. The alloy has a molybdenum equivalent weight MOeq of about 3.1 to about 4.4, where MO _eq is defined as follows:
The titanium alloy according to claim 1, wherein Mo, V, Cr and Fe represent weight percentages of molybdenum, vanadium, chromium and iron, respectively, in the alloy. The titanium alloy of claim 5, wherein the alloy has a molybdenum equivalent weight MO _eq of about 3.8. The alloy has an aluminum equivalent Al _eq of about 8.3 to about 10.5, where Al _eq is defined as:
Al _eq = Al + 27O
The titanium alloy according to claim 1, wherein Al and O each represent a weight percentage of aluminum and oxygen in the alloy. The titanium alloy according to claim 7, wherein the alloy has an aluminum equivalent Al _eq of about 9.4. The alloy, beta transformation temperature T _beta is about 1732 ° F~ about 1820 ° F, a titanium alloy according to claim 1. The titanium alloy of claim 9, wherein the alloy has a β transformation temperature _Tβ of about 1775 ° F. The titanium alloy according to claim 1, wherein the maximum concentration of any impurity element present in the titanium alloy is 0.1 wt%, and the combined concentration of all impurities is 0.4 wt% or less. The alloy has a tensile yield strength of at least about 120, both in the longitudinal and transverse directions.
The titanium alloy of claim 1, wherein the titanium alloy is 000 psi and has a maximum tensile strength of at least about 128,000 psi, a cross-sectional reduction of at least about 43%, and an elongation of at least about 12%.   A plate comprising the titanium alloy according to claim 1. 14. The plate of claim 13, wherein the thickness of the plate is between about 0.425 inches and about 0.450 inches. The plate has a ballistic limit V ₅₀ of at least about 1,848Fps, plate of claim 14. The plate has a thickness of about 0.430 inches and a ballistic limit V ₅₀ of about 1936 fps.
5. The plate according to 5. In a cold hearth furnace, a step of melting a composite of recycled materials containing aluminum, vanadium, iron, and titanium in an appropriate ratio to form a molten alloy, and a step of putting the molten alloy into a mold Basically, 4.2 to 5.4% aluminum by weight, 2.5 to
A method for producing a titanium alloy comprising 3.5% vanadium, 0.5-0.7% by weight iron, 0.15-0.19% by weight oxygen and the balance titanium. The method of claim 17, wherein the recycled material comprises 64 titanium dala powder, sponge titanium, iron and aluminum shot. 19. The recycled material according to claim 18, wherein the recycled material comprises about 70.4% 64 titanium Dalai powder, about 28.0% titanium sponge, about 0.4% iron and about 1.1% aluminum shot. Method. 19. The method of claim 18, wherein the recycled material comprises 64 titanium Dalai powder, commercial pure titanium scrap and sponge high iron. The method of claim 17, wherein the molten alloy is cast in a rectangular mold to form a slab having a rectangular shape. Further, the slab includes an initial rolling at a temperature higher than the β transformation temperature and a final rolling at a temperature lower than the β transformation temperature, and a step of finish annealing the plate at a temperature lower than the β transformation temperature. The method of claim 21, wherein: 23. The method of claim 22, wherein the finish annealing is at 1400 [deg.] F. and the plate is cooled to room temperature in an air atmosphere.