TW201708555A - High strength alpha/beta titanium alloy - Google Patents

Abstract

An alpha/beta titanium alloy comprising, in percent by weight based on total alloy weight: 3.9 to 4.5 aluminum; 2.2 to 3.0 vanadium; 1.2 to 1.8 iron; 0.24 to 0.30 oxygen; up to 0.08 carbon; up to 0.05 nitrogen; up to 0.015 hydrogen; titanium; and up to a total of 0.30 of other elements. A non-limiting embodiment of the alpha/beta titanium alloy comprises an aluminum equivalent value in the range of 6.4 to 7.2, exhibits a yield strength in the range of 120 ksi (827.4 MPa) to 155 ksi (1,069 MPa), exhibits an ultimate tensile strength in the range of 130 ksi (896.3 MPa) to 165 ksi (1,138 MPa), and exhibits a ductility in the range of 12 to 30 percent elongation.

Description

High strength α/β titanium alloy

This invention relates to high strength ductile alpha/beta titanium alloys.

Cross-reference to related applications

This application is a partial application. The case is based on 35 USC § 120 and is filed on October 13, 2010 and is entitled “High Strength Alpha/beta Titanium Alloy Fasteners and High Strength Alpha/Beta Titanium Alloy Fasteners and The benefit of the present application is the priority of U.S. Patent Application Serial No. 12/903,851, which is incorporated herein by reference. The priority of U.S. Patent Application Serial No. 12/888,699, the entire disclosure of which is incorporated herein by reference. The entire disclosure of the application Serial Nos. 12/903,851 and 12/888,699 is incorporated herein by reference.

Titanium alloys typically exhibit high strength to weight ratios, are corrosion resistant and resist creep at moderate temperatures. Titanium alloys are therefore used in aerospace, aerospace, defense, marine, and automotive applications, including, for example, landing gear components, frames, body armor, hulls, and mechanical fasteners.

Reducing the weight of an aircraft or other moving vehicle saves fuel. Thus, for example, the aerospace industry has tremendous power to reduce aircraft weight. Titanium and titanium alloys are attractive materials for weight reduction in aircraft applications due to their high strength to weight ratio. Most titanium alloy parts used in aerospace applications are made of Ti-6Al-4V alloy (ASTM Class 5; UNS) R56400; AMS 4928, AMS 4911) made of an alpha/beta titanium alloy.

Ti-6Al-4V alloy is one of the most common titanium-based materials and is estimated to account for more than 50% of the entire titanium-based material market. Ti-6Al-4V alloys are used in many applications that benefit from the advantageous combination of light weight, corrosion resistance and high strength at low to medium temperatures. For example, Ti-6Al-4V alloys are used in the manufacture of aircraft engine components, aircraft structural components, fasteners, high performance automotive components, medical device components, sports equipment, marine application components, and chemical processing equipment components.

The rolled product of Ti-6Al-4V alloy is generally used in a rolling annealing state or in a solution treatment and aging (STA) state. As used herein, "rolling annealing state" refers to the state of the titanium alloy after "rolling annealing" heat treatment, wherein the workpiece is annealed at a high temperature (for example, 1200-1500 °F / 649-816 ° C) about 1-8 Hour and cool in still air. After the workpiece is thermally processed in the α + β phase region, a rolling annealing heat treatment is performed. At room temperature, the minimum specified ultimate tensile strength of a Ti-6Al-4V alloy round rod having a diameter of about 2 to 4 吋 (5.08 to 10.16 cm) is 130 ksi (896 MPa) and a minimum specified yield at a rolling annealed condition. The strength is 120 ksi (827 MPa). Rolling annealed Ti-6Al-4V sheets are typically manufactured according to specification AMS 4911, while rolling annealed Ti-6Al-4V rods are typically manufactured according to specification AMS 4928.

U.S. Pat. % iron, 0.20 to 0.30% by weight of oxygen, incidental impurities and titanium. The alpha/beta titanium alloy disclosed in the '655 patent is referred to herein as "the '655 alloy." The commercially available alloy composition in the '655 alloy nominally includes 4.00% by weight aluminum, 2.50% by weight iron, 1.50% by weight iron, 0.25% by weight oxygen, incidental impurities, and titanium, and may be referred to herein as the total alloy weight. It is a Ti-4Al-2.5V-1.5Fe-0.25O alloy.

Since it is difficult to cold-process the Ti-6Al-4V alloy, the alloy is generally processed at a high temperature, generally above the α ₂ solvus temperature (for example, forging, rolling, drawing, and the like). The Ti-6Al-4V alloy increases strength because it has a high incidence of cracking (i.e., workpiece breakage) during cold deformation and cannot be effectively cold worked. However, as described in U.S. Patent Application Publication No. 2004/0221929, which is incorporated by reference in its entirety, it is surprisingly and unexpectedly found that the '655 alloy has a considerable cold deformability/ Cold workability.

The '655 alloy is surprisingly cold workable to achieve high strength while still retaining processable elongation. Processable ductility is defined herein as the state in which the alloy exhibits an elongation greater than 6%. Moreover, the strength of the '655 alloy is comparable to the strength that can be achieved with the Ti-6Al-4V alloy. For example, as shown in Table 6 of the '655 patent, the tensile stress measured for the Ti-6Al-4V alloy is 145.3 ksi (1,002 MPa), while the test sample for the '655 alloy is shown at 138.7 ksi to 142.7. Tensile strength in the range of ksi (956.3 MPa to 983.9 MPa).

The chemical composition range specified by aerospace material specification 6946B (AMS 6946B) is more limited than that described in the '655 patent application. The alloys specified in AMS 6946B retain a broader range of formability in the '655 patent, but the minimum mechanical strength properties allowed by AMS 6946B are below the minimum values specified for commercially available Ti-6Al-4V alloys. For example, according to AMS-4911L, the 0.125 inch (3.175 mm) thick Ti-6Al-4V plate has a minimum tensile strength of 134 ksi (923.9 MPa) and a minimum yield strength of 126 ksi (868.7 MPa). In contrast, according to AMS 6946B, the minimum tensile strength of 0.125 吋 (3.175 mm) thick Ti-4Al-2.5V-1.5Fe-0.25O sheet is 130 ksi (896.3 MPa) and the minimum yield strength is 115 ksi (792.9 MPa). ).

Assuming that there is still a need to reduce fuel consumption by mitigating the weight of aircraft and other vehicles, there is a need for improved ductile alpha/beta titanium alloys that preferably exhibit similar or superior performance to Ti-6Al-4V alpha/beta titanium alloys. Mechanical properties of mechanical properties.

According to one aspect of the invention, the alpha/beta titanium alloy comprises: 3.9 to 4.5 wt% aluminum; 2.2 to 3.0 wt% vanadium; 1.2 to 1.8 wt% iron; 0.24 to 0.30 wt% oxygen; 0.08 wt% carbon; up to 0.05 wt% nitrogen; up to 0.015 wt% hydrogen; titanium; and up to a total of 0.30 wt% other elements.

According to another aspect of the invention, the alpha/beta titanium alloy consists essentially of 3.9 to 4.5 wt% aluminum; 2.2 to 3.0 wt% vanadium; 1.2 to 1.8 wt% iron; 0.24 to 0.30, based on the weight of the total alloy. % by weight of oxygen; up to 0.08% by weight of carbon; up to 0.05% by weight of nitrogen; up to 0.015% by weight of hydrogen; titanium; and up to a total of 0.30% by weight of other elements.

1 is a graph of ultimate tensile strength and yield strength versus aluminum equivalent for a rod and wire comprising a non-limiting embodiment of the alloy of the present invention; and FIG. 2 is a 0.5 非 non-limiting example of an alloy comprising the present invention. (1.27 cm) diametrical line of ultimate tensile strength and yield strength versus aluminum equivalent; and Figure 3 is a tensile strength of a 1 吋 (2.54 cm) thick plate comprising a non-limiting embodiment of the alloy of the present invention, Graph of yield strength and elongation % versus aluminum equivalent.

The features and advantages of the alloys and related methods described herein are fully understood by reference to the drawings.

The above details and other details of certain non-limiting embodiments of the alloys and related methods of the present invention will be appreciated by the reader upon consideration of the following embodiments.

In the description of the non-limiting embodiments of the present invention, unless otherwise indicated herein, Accordingly, any numerical parameters set forth in the following description are approximations unless otherwise indicated, which may vary depending upon the nature of the material desired to be obtained by the method of the present invention. The application of the minimal and undesired doctrine of equivalents is limited to the scope of the patent application, and the numerical parameters should be understood at least in accordance with the number of significant digits reported and by applying the general rounding technique.

Any patents, publications, or other disclosures that are incorporated herein by reference in their entirety are hereby incorporated by reference to the extent of the extents Or other revealing material conflicts. Therefore, if necessary, such as In the event that the disclosure herein is inconsistent with any of the materials incorporated by reference, the disclosure herein is subject to the disclosure. Any material or a portion thereof or a portion thereof that is incorporated herein by reference but that conflicts with the existing definitions, statements, or other disclosure materials described herein is only incorporated to the extent that the Reveal the conflict between materials.

Non-limiting examples of the alpha/beta titanium alloy of the present invention comprise, consist of, or consist essentially of: 3.9 to 4.5 wt% aluminum; 2.2 to 3.0 wt% vanadium; 1.2 to 1.8 wt% iron; 0.24 to 0.30% by weight of oxygen; up to 0.08% by weight of carbon; up to 0.05% by weight of nitrogen; up to 0.015% by weight of nitrogen; titanium; and up to a total of 0.30% by weight of other elements. In certain non-limiting embodiments of the invention, other elements that may be present in the alpha/beta titanium alloy (as part of up to 0.30% by weight of other elements) include boron, tin, zirconium, molybdenum, chromium, nickel, niobium. And one or more of copper, ruthenium, osmium, manganese, ruthenium and cobalt, and in certain non-limiting embodiments, each of the other elements has a weight content of 0.10 or less, but with two exceptions . The exceptions are boron and bismuth, which are present in individual concentrations of less than 0.005% by weight if they are present wholly as part of one of the other elements.

I. Alloy composition

Non-limiting examples of alloys of the present invention include titanium, aluminum, vanadium, iron, and oxygen. As long as the alloying elements are stated in the composition of the following discussion, it should be understood that the remainder includes titanium and incidental impurities.

A. Aluminum

Aluminum is an alpha phase enhancer in titanium alloys. In a non-limiting embodiment of the alpha/beta titanium alloy of the present invention, the compositional range of aluminum is narrower than the range of aluminum disclosed in the '655 patent. Again, the minimum content of aluminum in certain non-limiting embodiments of the alloys according to the present invention is greater than the minimum levels described in AMS 6946B. These compositional characteristics have been observed to make the alloy exhibit a more consistent mechanical properties similar to those of the Ti-6Al-4V alloy. The minimum concentration of aluminum in the α/β titanium alloy of the present invention is 3.9% by weight. The maximum concentration of aluminum in the α/β titanium alloy of the present invention is 4.5% by weight.

B. Vanadium

Vanadium is a beta phase stabilizer in titanium alloys. The minimum concentration of vanadium in the alpha/beta titanium alloy of the present invention is greater than the minimum concentration as disclosed in the '655 patent and as described in AMS 6946B. This compositional feature has been observed to provide an optimal, controlled balance of the volume fraction of the alpha phase and the beta phase. The balance of the alpha phase and the beta phase allows the alloy of the invention to have excellent ductility and formability. Vanadium is present in the alpha/beta titanium alloy of the present invention at a minimum concentration of 2.2% by weight. The maximum concentration of vanadium in the α/β titanium alloy of the present invention is 3.0% by weight.

C. Iron

Iron is an eutectoid beta stabilizer in titanium alloys. The alpha/beta titanium alloy of the present invention comprises a greater minimum concentration and a narrower range of iron than the alloys described in the '655 patent. These characteristics have been observed to provide an optimal, controlled balance of the volume fraction of the alpha phase and the beta phase. This balance allows the alloy of the present invention to have excellent ductility and formability. Iron is present in the alpha/beta alloy of the present invention at a minimum concentration of 1.2% by weight. The maximum concentration of iron in the α/β titanium alloy of the present invention is 1.8% by weight.

D. Oxygen

Oxygen is an alpha phase enhancer in titanium alloys. The composition range of oxygen in the α/β titanium alloy of the present invention is narrower than that disclosed in the '655 patent and the AMS 6946B specification. Again, the minimum concentration of oxygen in the non-limiting embodiment of the alloy of the present invention is greater than the minimum concentration in the '655 patent and AMS 6946B specifications. These compositional features have been observed to allow the alloys of the present invention to consistently exhibit mechanical properties similar to those of certain Ti-6Al-4V mechanical properties. The minimum concentration of oxygen in the α/β titanium alloy of the present invention is 0.24% by weight. The maximum concentration of oxygen in the α/β titanium alloy of the present invention is 0.30% by weight.

In addition to including titanium, aluminum, vanadium, iron, and oxygen as discussed above, certain non-limiting examples of the alpha/beta titanium alloys of the present invention include other elements having a total concentration of no more than 0.30% by weight. In certain non-limiting embodiments, such other elements include one or more of boron, tin, zirconium, molybdenum, chromium, nickel, ruthenium, copper, ruthenium, osmium, manganese, ruthenium, and cobalt, with the exception of two One Exceptionally, the weight % of each such element is 0.10 or less than 0.10. The exceptions are boron and antimony. If present in the alloy of the present invention, the weight percent of each of boron and rhodium is less than 0.005.

The incidental impurities may also be present in the α/β titanium alloy of the present invention. For example, up to about 0.008% by weight carbon can be present. There may be up to about 0.05% by weight nitrogen. There may be up to about 0.015% by weight hydrogen. Other incidental impurities that may be present will be apparent to those of ordinary skill in the art of metallurgy.

Table 1 provides a summary of (i) certain non-limiting examples of the alpha/beta titanium alloys of the present invention and (ii) the compositions of certain alloys as disclosed in the '655 patent and as specified in AMS 6946B.

The inventors have unexpectedly discovered that alloys of the present invention that provide a minimum level of aluminum, oxygen, and iron greater than the minimum levels taught in the '655 patent can provide consistent display of, for example, at least annealed Ti-6Al-4V alloys. Some α/β titanium alloys with similar mechanical properties (such as strength). The inventors have also unexpectedly discovered that it is disclosed in relation to the '655 patent. Their minimum and range, increasing the minimum content of iron and vanadium and narrowing their range provide an alloy that exhibits the best and controlled balance of the volume fraction of the alpha and beta phases in the rolling annealed form. This optimum phase balance of the alpha/beta titanium alloy of the present invention provides an alloying example that is more ductile than the Ti-6Al-4V alloy while retaining the ductility of the alloys as disclosed in the '655 patent and as specified in AMS 6946B.

Those skilled in the art understand that the strength and ductility of metallic materials generally exhibit an inverse relationship. In other words, in general, as the strength of the metal material increases, the ductility of the material decreases. Since the inverse relationship between strength and ductility is generally observed for roll-rolled annealed titanium alloys, the α/β titanium alloy of the present invention is not expected to have a combination of increased mechanical strength and retained ductility. The unexpected and surprising combination of increased mechanical strength and retained ductility is a particularly advantageous feature of the alloy embodiments of the present invention. Surprisingly, it has been observed that the embodiment of the roll-annealed alloy of the present invention exhibits comparable strength to the Ti-6Al-4V alloy without exhibiting a decrease in ductility.

Certain non-limiting examples of the alpha/beta alloys of the present invention having an aluminum equivalent value (Al _eq ) of at least 6.3 or more preferably at least 6.4 have been observed to exhibit strengths at least comparable to those of Ti-6Al-4V alloys. . It has also been observed that these alloys exhibit ductility superior to Ti-6Al-4V alloys having an aluminum equivalent value of typically about 7.5. As used herein, "aluminum equivalent value" or "aluminum equivalent" (Al _eq ) means a value equal to 10 times the concentration of aluminum in the alloy (% by weight) plus the oxygen concentration (% by weight) in the alloy. In other words, the aluminum equivalent of the alloy can be determined as follows: Al _eq = Al _(wt.%) + 10 (O _(wt.%) ).

While recognizing that the mechanical properties of titanium alloys are generally affected by the size of the sample being tested, in a non-limiting embodiment of the invention, the alpha equivalent of the alpha/beta titanium alloy is at least 6.4, or in certain embodiments The range is in the range of 6.4 to 7.2, and the yield strength is at least 120 ksi (827.4 MPa), or in some embodiments at least 130 ksi (896.3 MPa).

In other non-limiting embodiments of the invention, the alpha/beta titanium alloy has an aluminum equivalent value of at least 6.4, or in certain embodiments, in the range of 6.4 to 7.2, and a yield strength of 120. Ksi (827.4 MPa) to 155 ksi (1,069 MPa).

In other non-limiting embodiments, the alpha/beta titanium alloy of the present invention has an aluminum equivalent value of at least 6.4, or in certain embodiments, in the range of 6.4 to 7.2, and an ultimate tensile strength of at least 130 ksi ( 896.3 MPa), or in some embodiments at least 140 ksi (965.3 MPa).

In other non-limiting embodiments of the invention, the alpha/beta titanium alloy of the invention has an aluminum equivalent weight of at least 6.4, or in certain embodiments in the range of 6.4 to 7.2, and an ultimate tensile strength at It is in the range of 130 ksi (896.3 MPa) to 165 ksi (1,138 MPa).

In other non-limiting embodiments, the alpha/beta titanium alloy of the present invention has an aluminum equivalent value of at least 6.4, or in certain embodiments, in the range of 6.4 to 7.2, and ductility of at least 12% or at least 16 %(Elongation%).

In other non-limiting embodiments, the alpha/beta titanium alloys of the present invention have an aluminum equivalent weight of at least 6.4, or in certain embodiments from 6.4 to 7.2, and ductility of from 12% to 30% ( Elongation % or "% el").

Although 6.3 is the absolute minimum of Al _{eq in} accordance with certain non-limiting embodiments of the present invention, the inventors have determined that an Al _eq value of at least 6.4 is required to achieve the same strength as exhibited by the Ti-6Al-4V alloy. strength. It is also recognized that in other non-limiting embodiments of the alpha/beta titanium alloy of the present invention, the maximum value of Al _eq is 7.5 and the relationship between strength and ductility in accordance with other non-limiting embodiments disclosed herein applies.

According to one non-limiting embodiment, the alpha/beta titanium alloy of the present invention has an aluminum equivalent value of at least 6.4, a yield strength of at least 120 ksi (827.4 MPa), an ultimate tensile strength of at least 130 ksi (896.3 MPa), and ductility. At least 12% (elongation %).

According to another non-limiting embodiment, the alpha/beta titanium alloy of the present invention has an aluminum equivalent value of at least 6.4, a yield strength of at least 130 ksi (896.3 MPa), an ultimate tensile strength of at least 140 ksi (965.3 MPa), and ductility. At least 12%.

In yet another non-limiting embodiment, the alpha equivalent of the alpha/beta titanium alloy of the present invention is at 6.4 Within the range of 7.2, the yield strength is in the range of 120 ksi (827.4 MPa) to 155 ksi (1,069 MPa), the ultimate tensile strength is in the range of 130 ksi (896.3 MPa) to 165 ksi (1,138 MPa), and the ductility is 12% to Within 30% (elongation %).

In one non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average ultimate tensile strength (UTS) that satisfies the following equation: UTS 14.767 (Al _eq ) + 48.001.

In another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average yield strength (YS) that satisfies the following equation: YS 13.338 (Al _eq ) + 46.864.

In yet another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits the following average ductility: %el 3.3669 (Al _eq )-1.9417.

In another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average ultimate tensile strength (UTS) that satisfies the following equation: UTS 14.767(Al _eq )+48.001; the average yield strength (YS) satisfying the following equation: YS 13.338(Al _eq )+46.864; and satisfy the average ductility of the following equation: %el 3.3669 (Al _eq )-1.9417.

In one non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average ultimate tensile strength (UTS) that satisfies the following equation: UTS 12.414 (Al _eq ) + 64.429.

In another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average yield strength (YS) that satisfies the following equation: YS 13.585 (Al _eq ) + 44.904.

In yet another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits the following average ductility: %el 4.1993 (Al _eq ) + 7.4409.

In another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average ultimate tensile strength (UTS) that satisfies the following equation: UTS 12.414(Al _eq )+64.429; the average yield strength (YS) satisfying the following equation: YS 13.585(Al _eq )+44.904; and satisfy the average ductility of the following equation: %el 4.1993 (Al _eq ) + 7.4409.

In one non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average ultimate tensile strength (UTS) that satisfies the following equation: UTS 10.087 (Al _eq ) + 76.785.

In another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average yield strength (YS) that satisfies the following equation: YS 13.911 (Al _eq ) + 39.435.

In yet another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits the following average ductility: %el 1.1979(Al _eq )+8.5604.

In yet another non-limiting embodiment, the alpha/beta titanium alloy of the present invention exhibits an average ultimate tensile strength (UTS) that satisfies the following equation: UTS 10.087(Al _eq )+76.785; the average yield strength (YS) satisfying the following equation: YS 13.911(Al _eq )+39.435; and the unit of the following equation is the average ductility of elongation % (%el): %el 1.1979(Al _eq )+8.5604.

It has been determined that non-limiting examples of the alpha/beta titanium alloys of the present invention exhibit similar or higher mechanical strength, higher ductility, and improved formability than Ti-6Al-4V alloys. Therefore, it is possible to use articles formed from the alloy of the present invention as an alternative to Ti-6Al-4V alloy articles in aerospace, aerospace, marine, automotive, and other applications. The high strength and ductility of the examples of the alloys of the present invention allow for the manufacture of high tolerance and are currently not available from Ti-6Al- Some rolled finished shapes made of 4V alloy.

One aspect of the invention pertains to articles comprising the alloy of the invention and/or articles made from the alloys of the invention. Certain non-limiting embodiments of such articles may be selected from the group consisting of aircraft engine components, aircraft structural components, automotive components, medical device components, sports equipment components, marine application components, and chemical processing equipment components. The alpha/beta titanium alloy embodiments of the present invention and/or other articles made therefrom, which are known to those of ordinary skill in the art and which may be included herein, are within the scope of the embodiments disclosed herein. Articles comprising the alloy of the invention and/or alloys of the invention by forming and other manufacturing techniques are now or will be known to those of ordinary skill in the art.

The following examples are intended to further describe certain non-limiting embodiments without limiting the scope of the invention. It will be appreciated by those skilled in the art that variations of the following examples, and other embodiments not specifically described herein, may be present within the scope of the invention as defined by the appended claims.

Example 1

The α/β titanium alloy ingot having the composition of the present invention is cast by conventional vacuum arc remelting (VAR), plasma arc melting (PAM) or electron beam cold crucible melting (EB), and VAR is used again. melt. The composition of the ingot is included in the range listed in the column "Non-Limited Embodiments of the Invention" in Table 1 above.

The ingot composition produced in this Example 1 had an aluminum equivalent value ranging from about 6.0 to about 7.1. The ingot was processed into hot rolled bars and wires having a diameter between 0.25 吋 (0.635 cm) and 3.25 吋 (8.255 cm) using various hot rolling operations. Hot rolling was carried out at an initial temperature between 1550 °F (843.3 °C) and 1650 °F (898.9 °C). This temperature range is lower than the alpha/beta transition temperature of the alloy of this example, which is from about 1750 °F to about 1850 °F (about 954.4 °C to about 1010 °C), depending on the actual chemical composition. After hot rolling, the hot rolled bars and wires were annealed at 1275 °F (690.6 °C) for 1 hour, followed by air cooling. The diameters, aluminum concentrations, iron concentrations, oxygen concentrations, and calculated Al _eq of the rod and line samples produced in Example 1 are provided in Table 2.

Figure 1 graphically shows the room temperature ultimate tensile strength (UTS), yield strength (YS), and elongation % (%el) of the rod and wire samples listed in Table 2 and the aluminum equivalent value of the alloy in the sample. relationship. Figure 1 also includes trend lines that pass through the UTS, YS, and %el data points as determined by linear regression. It can be seen that both the average intensity and the average elongation % increase with increasing Al _eq . This relationship is surprising and unexpected because it is contrary to the generally observed relationship of increased strength with reduced ductility.

Typical UTS and YS minimum values for Ti-6Al-4V are 135 ksi (930.8 MPa) and 125 ksi (861.8 MPa), respectively. The YS range of the inventive samples listed in Table 2 ranged from about 125 ksi (for samples with Al _eq of about 6.0) to about 141 ksi (samples with about 7.1 for Al _eq ). A sample with an Al _eq of about 6.4 exhibited a YS of about 130 ksi (896.3 MPa). The UTS of the inventive samples listed in Table 2 ranged from about 135 ksi (for samples with Al _eq of about 6.0) to about 153 ksi (samples with about 7.1 for Al _eq ). A sample with an Al _eq of about 6.4 exhibited a YS of about 141 ksi (972 MPa).

Example 2

Tensile tests were carried out on line samples Nos. 9-11 of Example 1 having a diameter of 0.5 Å (1.27 cm) and an aluminum equivalent value of about 6.5, about 6.8, and about 7.15 at room temperature. The results of the tensile test are shown graphically in Figure 2. All of these samples exhibited tensile and yield strengths similar to or higher than those exhibited by commercial Ti-6Al-4V alloys. As can be seen from Figure 1, the increase in Al _{eq results in} an increase in strength and an increase in the average elongation %. As discussed above, this trend is surprising and unexpected because it is contrary to the generally observed relationship of increased strength with reduced ductility. The data spread of Figure 2, which represents the test performed on samples of the same size, is smaller compared to Figure 1 which represents tests performed on samples of various sizes, since the mechanical properties are somewhat affected by the size of the test sample.

Example 3

A hot rolled 1 吋 (2.54 cm) thick plate sample was made from the ingot made according to the procedure described in Example 1. The alloy ingot has a composition within the range listed in the "Non-Limited Examples of the Invention" column of Table 1 above, wherein the aluminum and oxygen concentrations and aluminum equivalent values are as listed in Table 3.

All hot rolling temperatures are below the alpha/beta transition temperature of the alloy. The alloy has an Al _eq value of from about 6.5 to about 7.1. Tensile strength, yield strength, and elongation % (ductility) were measured using a room temperature tensile test. The tensile test results are shown graphically in Figure 3. As can be seen from Figure 3, the alloys including the increased levels of Al and O exhibited at least room strength at room temperature as indicated by the calculated aluminum equivalents, at least comparable to the strength exhibited by the Ti-6Al-4V alloy. In addition, it was observed that the intensity increased as the Al _eq increased. In addition, the average ductility of the alloys of the present invention increases slightly or remains substantially constant as Al _eq increases and strength increases. This trend is surprising and unexpected because it is contrary to the generally observed relationship of increased strength with reduced ductility.

The invention has been described with reference to various exemplary, illustrative and non-limiting embodiments. However, it is to be understood by those skilled in the art that the invention may be substituted, modified, or combined with any of the disclosed embodiments (or a portion thereof) without departing from the scope of the invention. Therefore, it is contemplated and appreciated that the invention encompasses other embodiments not specifically described herein. The embodiments can be obtained, for example, by combining and/or modifying any of the disclosed steps, ingredients, components, components, elements, features, aspects, and the like. Accordingly, the invention is to be limited by the description of the invention, In this manner, it is to be understood that the scope of the patent application can be modified during the review of the present patent application to add to the present invention features as described herein in various ways.

Claims (11)

An α/β titanium alloy comprising, by weight of the total alloy, 4.05 to 4.40% by weight of aluminum; 2.2 to 3.0% by weight of vanadium; 1.24 to 1.56% by weight of iron; 0.24 to 0.28% by weight of oxygen; up to 0.08% by weight of carbon Up to 0.05% by weight of nitrogen; up to 0.015% by weight of hydrogen; titanium; and up to 0.30% by weight of other elements; wherein the alloy comprises an aluminum equivalent value of at least 6.4, exhibiting a yield strength of at least 122 ksi (841.2 MPa), Showing an ultimate tensile strength of at least 142 ksi (979.1 MPa) and exhibiting a ductility of at least 20% elongation; and an average yield strength and an average ultimate tensile strength when the aluminum equivalent value is increased to a range of 6.4 to 7.2 Increase, and the average ductility does not decrease. The α/β titanium alloy of claim 1, wherein: at most a total of 0.30% by weight of other elements include boron, tin, zirconium, molybdenum, chromium, nickel, niobium, copper, lanthanum, cerium, manganese, lanthanum and cobalt. At least one; in the presence of, each of boron and bismuth is less than 0.005% by weight; and in the presence of each of tin, zirconium, molybdenum, chromium, nickel, ruthenium, copper, osmium, iridium, manganese, and cobalt The content is not more than 0.10% by weight. The α/β titanium alloy of claim 1, wherein the alloy has an aluminum equivalent value in the range of 6.4 to 7.2 and exhibits a yield strength in the range of 122 ksi (841.2 MPa) to 155 ksi (1,069 MPa). The α/β titanium alloy of claim 1, wherein the alloy has an aluminum equivalent value in the range of 6.4 to 7.2 and exhibits an ultimate tensile strength in the range of 142 ksi (979.1 MPa) to 165 ksi (1,138 MPa). The α/β titanium alloy of claim 1, wherein the alloy has an aluminum equivalent value in the range of 6.4 to 7.2 and exhibits ductility in the range of 20% to 30% elongation. The α/β titanium alloy of claim 1, wherein the alloy has an aluminum equivalent value in the range of 6.4 to 7.2, exhibiting a yield strength in the range of 122 ksi (841.2 MPa) to 143.1 ksi (986.6 MPa), which is exhibited in The ultimate tensile strength in the range of 142.3 ksi (981.1 MPa) to 154.6 ksi (1,066 MPa) and exhibits ductility in the range of 20% to 22% elongation. The α/β titanium alloy of claim 1, wherein the average ultimate tensile strength (UTS) of the α/β titanium alloy in ksi satisfies the following equation: UTS 14.767(Al _eq )+48.001, the standard deviation is 0.6213; wherein the average yield strength (YS) of the α/β titanium alloy in ksi satisfies the following equation: YS 13.338(Al _eq )+46.864; the standard deviation is 0.4519; and wherein the average ductility of the α/β titanium alloy measured by % elongation satisfies the following equation: %el 3.3669 (Al _eq )-1.9417, standard deviation is 0.1746; where Al _eq = aluminum weight percent + 10 (oxygen) weight percent. The α/β titanium alloy of claim 1, wherein the average ultimate tensile strength (UTS) of the α/β titanium alloy in ksi satisfies the following equation: UTS 12.414(Al _eq )+64.429, the standard deviation is 0.9576; wherein the average yield strength (YS) of the α/β titanium alloy in ksi satisfies the following equation: YS 13.585 (Al _eq )+44.904; standard deviation is 0.8138; and wherein the average ductility measured by % elongation of the α/β titanium alloy satisfies the following equation: %el 4.1993 (Al _eq )-7.4409, standard deviation is 0.1731; where Al _eq = aluminum weight percent + 10 (oxygen) weight percent. The α/β titanium alloy of claim 1, wherein the average ultimate tensile strength (UTS) of the α/β titanium alloy in ksi satisfies the following equation: UTS 10.087(Al _eq )+76.785; wherein the average yield strength (YS) of the α/β titanium alloy in ksi satisfies the following equation: YS 13.911(Al _eq )+39.435; and wherein the average ductility of the α/β titanium alloy measured by % elongation satisfies the following equation: %el 1.1979(Al _eq )+8.5604; wherein Al _eq = aluminum weight percent + 10 (oxygen) weight percent. An article comprising the alloy of claim 1. The article of claim 10, wherein the article is selected from the group consisting of an aircraft engine component, an aircraft structural component, an automotive component, a medical device component, a sports equipment component, a marine application component, and a chemical processing equipment component.