TWI631222B - High strength alpha/beta titanium alloy - Google Patents

Abstract

The present invention provides an α / β titanium alloy, based on the total alloy weight, comprising: 3.9 to 4.5% by weight aluminum; 2.2 to 3.0% by weight vanadium; 1.2 to 1.8% by weight iron; 0.24 to 0.30% by weight oxygen; up to 0.08% by weight % Carbon; up to 0.05% by weight nitrogen; up to 0.015% by weight hydrogen; titanium; and up to a total of 0.30% by weight of other elements. A non-limiting example of this α / β titanium alloy has an aluminum equivalent value in a range of 6.4 to 7.2, exhibits a yield strength in a range of 120 ksi (827.4 MPa) to 155 ksi (1,069 MPa), and exhibits a strength of 130 ksi ( 896.3 MPa) to 165 ksi (1,138 MPa) in the ultimate tensile strength, and exhibits ductility in the range of 12% to 30% elongation.

Description

High-strength α / β titanium alloy

The present invention relates to a high-strength ductile α / β titanium alloy.

Cross-reference to related applications

This application is part of a continuation application. This application claims that it was filed on October 13, 2010 and named "High Strength Alpha / Beta Titanium Alloy Fasteners and "Fastener Stock)" has the same priority as US Patent Application No. 12 / 903,851 in the same application, which is a partial continuation application, claiming that it was filed on September 23, 2010 under the name "High High strength alpha / beta titanium alloy fasteners and fastener materials ("High Strength Alpha / Beta Titanium Alloy Fasteners and Fastener Stock") have the same priority as US Patent Application No. 12 / 888,699 in the application. The entire disclosures of Application Nos. 12 / 903,851 and 12 / 888,699 are incorporated herein by reference.

Titanium alloys typically exhibit high strength-to-weight ratios, corrosion resistance, and creep resistance at moderately high temperatures. Therefore, titanium alloys are used in aerospace, aviation, defense, marine and automotive applications, including, for example, landing gear components, frames, body armor, hulls, and mechanical fasteners.

Reducing the weight of aircraft or other moving vehicles can save fuel. So, for example, the aerospace industry has tremendous power to reduce aircraft weight. Titanium and titanium alloys are attractive materials for achieving 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 level 5; UNS R56400; AMS 4928, AMS 4911), which is an α / β titanium alloy.

Ti-6Al-4V alloy is one of the most common titanium-based manufacturing materials, and it is estimated that it accounts 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 the alloy's light weight, corrosion resistance, and high strength at low to medium temperatures. For example, Ti-6Al-4V alloy is used to manufacture aircraft engine components, aircraft structural components, fasteners, high-performance automotive components, medical device components, sports equipment, marine application components, and chemical processing equipment components.

Ti-6Al-4V alloy rolled products are generally used in the rolled annealing state or in the solution treatment and aging (STA) state. As used herein, "rolled annealed state" refers to the state of the titanium alloy after the "rolled annealing" heat treatment, in which the workpiece is annealed at a high temperature (for example, 1200-1500 ° F / 649-816 ° C) for about 1-8 Hours and cooled in still air. After the workpiece is hot-worked in the α + β phase region, it is subjected to rolling annealing heat treatment. At room temperature, in the rolling annealed state, the minimum specified ultimate tensile strength of a Ti-6Al-4V alloy round rod with a diameter of about 2 to 4 inches (5.08 to 10.16 cm) is 130 ksi (896 MPa) and the minimum specified yield. The strength is 120ksi (827MPa). The rolled annealed Ti-6Al-4V plate is usually manufactured according to the specification AMS 4911, and the rolled annealed Ti-6Al-4V rod is usually manufactured according to the specification AMS 4928.

U.S. Patent No. 5,980,655 ("the '655 Patent"), which is incorporated herein by reference in its entirety, discloses an alpha / beta titanium alloy comprising 2.90 to 5.00 weight percent aluminum, 2.00 to 3.00 weight percent vanadium, 0.40 to 2.00 weight % Iron, 0.20 to 0.30% by weight 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 vanadium, 1.50% by weight iron, 0.25% by weight oxygen, incidental impurities, and titanium based on the total alloy weight, and may be referred to herein It is Ti-4Al-2.5V-1.5Fe-0.25O alloy.

Because it is difficult to cold-work Ti-6Al-4V alloys, the alloys are generally processed at high temperatures, generally above the α ₂ solid solution temperature (such as forging, rolling, drawing, and similar processing). The Ti-6Al-4V alloy cannot be effectively cold-worked to increase strength due to, for example, a high incidence of cracking (i.e., workpiece breakage) during cold deformation. However, as described in U.S. Patent Application Publication No. 2004/0221929, which is incorporated herein by reference in its entirety, it was surprisingly and unexpectedly discovered that the '655 alloy has a considerable degree of cold deformability / Cold workability.

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

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

Assuming that it is still necessary to reduce fuel consumption by reducing the weight of aircraft and other vehicles, an improved ductility α / β titanium alloy is required, which better displays similar or better than that shown by Ti-6Al-4V α / β titanium alloy. Mechanical properties.

According to one aspect of the present invention, the α / β titanium alloy comprises: 3.9 to 4.5% by weight of aluminum; 2.2 to 3.0% by weight of vanadium; 1.2 to 1.8% by weight of iron; 0.24 to 0.30% by weight of oxygen; based on the total alloy weight; at most 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 present invention, the α / β titanium alloy is basically composed of the following based on the total alloy weight: 3.9 to 4.5% by weight aluminum; 2.2 to 3.0% by weight vanadium; 1.2 to 1.8% by weight iron; 0.24 to 0.30 Up to 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.

FIG. 1 is a diagram showing the relationship between the ultimate tensile strength and yield strength of a rod and a wire including a non-limiting example of the alloy of the present invention and the aluminum equivalent; FIG. 2 is a 0.5 inch of the non-limiting example of the alloy of the present invention. (1.27cm) The relationship between the ultimate tensile strength and yield strength of the diameter line and the aluminum equivalent; and Figure 3 is a tensile strength of a 1-inch (2.54cm) thick plate including a non-limiting example of the alloy of the present invention. Relationship between yield strength and elongation% and aluminum equivalent.

The characteristics and advantages of the alloys and related methods described herein can be fully understood with reference to the drawings.

The reader will understand the above details and other details of some non-limiting examples of alloys and related methods of the present invention after considering the following embodiments.

In the description of non-limiting embodiments of the present invention, all numbers expressing quantities or features are to be understood as modified in all cases by the term "about", except in the operating examples or otherwise stated. Therefore, unless stated to the contrary, any numerical parameter described in the following description is approximate and can vary depending on the nature of the desired material sought to be obtained by the method of the present invention. The application of doctrine of equivalents is minimally and not intended to be limited to the scope of patent applications. Each numerical parameter should be understood at least based on the reported significant digits and by applying general rounding techniques.

Any reference to any patent, publication or other disclosure material incorporated herein by reference in its entirety or in part is incorporated herein only to the extent that the incorporated material is not inconsistent with the existing definitions, statements, or descriptions contained herein. Or other revealing material conflicts. Therefore, if necessary, such as In the event of a conflict between the disclosure described herein and any material incorporated by reference, the disclosure described herein shall prevail. References to any material, or part or part thereof, incorporated herein by reference but in conflict with existing definitions, statements or other disclosed materials described herein are incorporated to the extent only that the incorporated material is in conflict with the existing There is no conflict between revealed materials.

Non-limiting examples of the α / β titanium alloy of the present invention include the following, consisting of or consisting essentially of: 3.9 to 4.5% by weight aluminum; 2.2 to 3.0% by weight vanadium; 1.2 to 1.8% by weight iron; 0.24 to 0.30 wt% oxygen; up to 0.08 wt% carbon; up to 0.05 wt% nitrogen; up to 0.015 wt% nitrogen; titanium; and up to a total of 0.30 wt% other elements. In certain non-limiting embodiments of the invention, other elements that may be present in the α / β titanium alloy (as part of up to 0.30% by weight of other elements) include boron, tin, zirconium, molybdenum, chromium, nickel, silicon Or copper, niobium, tantalum, manganese, yttrium, and cobalt, and in certain non-limiting embodiments, each such other element has a weight content of 0.10 or less, with two exceptions . These exceptions are boron and yttrium, and if they exist entirely as part of other elements, they exist at individual concentrations of less than 0.005% by weight.

I. Alloy composition

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

A. Aluminum

Aluminum is an α-phase strengthening agent in titanium alloys. In the non-limiting embodiment of the α / β titanium alloy of the present invention, the composition range of aluminum is narrower than the aluminum range disclosed in the '655 patent. Also, the minimum content of aluminum in certain non-limiting embodiments of the alloy according to the present invention is greater than the minimum content described in AMS 6946B. It has been observed that these compositional characteristics allow the alloy to more consistently exhibit mechanical properties similar to those of 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 α / β titanium alloy of the present invention is greater than the minimum concentration disclosed in the '655 patent and described in AMS 6946B. This compositional feature has been observed to provide an optimal, controlled balance of volume fractions of the alpha and beta phases. The balance between the α phase and the β phase makes the alloy of the invention have excellent ductility and formability. Vanadium is present in the α / β 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 a eutectoid beta stabilizer in titanium alloys. Compared to the alloy described in the '655 patent, the α / β titanium alloy of the present invention includes a larger minimum concentration and a narrower range of iron. These characteristics have been observed to provide an optimal, controlled balance of volume fractions of the alpha and beta phases. This balance makes the alloy of the present invention excellent in ductility and formability. Iron is present in the α / β alloy of the present invention at a minimum concentration of 1.2% by weight. The maximum iron concentration in the α / β titanium alloy of the present invention is 1.8% by weight.

D. Oxygen

Oxygen is an α-phase strengthening agent 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. In addition, 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 the AMS 6946B specification. It has been observed that these compositional characteristics allow the alloys of the present invention to consistently exhibit mechanical properties similar to the mechanical properties of certain Ti-6Al-4V. 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 with a total concentration of no more than 0.30% by weight. In certain non-limiting embodiments, these other elements include one or more of boron, tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, yttrium, and cobalt, with the exception of two Each Exceptionally, the weight% of each of these elements is 0.10 or less. These exceptions are boron and yttrium. If present in the alloy of the present invention, the weight% of each of boron and yttrium is less than 0.005.

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 of carbon may be present. Nitrogen may be present up to about 0.05% by weight. Up to about 0.015% by weight hydrogen may be present. Other incidental impurities that may be present will be apparent to those skilled in the art of metallurgy.

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

The inventors have unexpectedly discovered that providing an alloy of the present invention with a minimum content of aluminum, oxygen, and iron greater than the minimum content taught in the '655 patent can provide a consistent display of, for example, at least the rolling annealed Ti-6Al-4V alloy Certain α / β titanium alloys with similar mechanical properties, such as strength. The inventors also unexpectedly found that, compared to what was disclosed in the '655 patent Their minimum values and ranges, increasing the minimum content of iron and vanadium, and narrowing their ranges can provide alloys that exhibit the best and controlled balance of volume fractions of the α phase and β phase in the form of rolled annealing. This optimal phase balance of the alpha / beta titanium alloy of the present invention provides an embodiment of the alloy that is more ductile than the Ti-6Al-4V alloy while retaining the ductility of the alloy disclosed in the '655 patent and specified in AMS 6946B.

Those familiar with this technology understand that the strength and ductility of metal materials generally show an inverse relationship. In other words, in general, as the strength of a metal material increases, the ductility of the material decreases. Because an inverse relationship between strength and ductility is generally observed for 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 embodiment of the invention. It was surprisingly observed that the examples of the rolled annealed alloys of the present invention exhibited a strength comparable to that of Ti-6Al-4V alloy without exhibiting a reduction in ductility.

It has been observed that 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 better and at least 6.4 exhibit strengths at least comparable to those of Ti-6Al-4V alloy . These alloys have also been observed to exhibit ductility over Ti-6Al-4V alloys with aluminum equivalent values typically of about 7.5. As used herein, "aluminum equivalent value" or "aluminum equivalent" (Al _eq ) means a value equal to 10 times the aluminum concentration (wt%) in the alloy plus the oxygen concentration (wt%) in the alloy. In other words, the aluminum equivalent of the alloy can be determined as follows: Al _eq = Al _(wt.%) +10 (O _(wt.%) ).

Although it is recognized that the mechanical properties of titanium alloys are generally affected by the size of the test specimen, in non-limiting embodiments of the invention, the aluminum equivalent value of the α / β titanium alloy is at least 6.4, or in some embodiments The range is from 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 present invention, the aluminum equivalent value of the α / β titanium alloy is at least 6.4, or in some embodiments in the range of 6.4 to 7.2, and the yield strength is 120 ksi (827.4MPa) to 155ksi (1,069MPa).

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

In other non-limiting embodiments of the present invention, the aluminum equivalent value of the α / β titanium alloy of the present invention is at least 6.4, or in some embodiments in the range of 6.4 to 7.2, and the ultimate tensile strength is between 130ksi (896.3MPa) to 165ksi (1,138MPa).

In other non-limiting embodiments, the aluminum equivalent value of the α / β titanium alloy of the present invention is at least 6.4, or in some embodiments in the range of 6.4 to 7.2, and the ductility is at least 12% or at least 16 %(Elongation%).

In other non-limiting embodiments, the aluminum equivalent value of the α / β titanium alloy of the present invention is at least 6.4, or in some embodiments in the range of 6.4 to 7.2, and the ductility is 12% to 30% ( Elongation% or "% el").

Although according to some non-limiting embodiments of the present invention, 6.3 is the absolute minimum of Al _eq , the inventors have determined that an Al _eq value of at least 6.4 is required to achieve the same strength as that exhibited by Ti-6Al-4V alloys strength. It is also recognized that in other non-limiting embodiments of the α / β titanium alloy of the present invention, the maximum value of Al _eq is 7.5 and the relationship between strength and ductility is applicable according to other non-limiting embodiments disclosed herein.

According to a non-limiting embodiment, the α / β 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 a ductility of At least 12% (% elongation).

According to another non-limiting embodiment, the α / β 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. Is at least 12%.

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

In a non-limiting example, the α / β 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 α / β 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 α / β titanium alloy of the present invention exhibits the following average ductility:% el 3.3669 (Al _eq ) -1.9417.

In another non-limiting example, the α / β 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; average yield strength (YS) satisfying the following equation: YS 13.338 (Al _eq ) +46.864; and average ductility satisfying the following equation:% el 3.3669 (Al _eq ) -1.9417.

In a non-limiting example, the α / β 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 α / β 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 α / β titanium alloy of the present invention exhibits the following average ductility:% el 4.1993 (Al _eq ) +7.4409.

In another non-limiting example, the α / β 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 average ductility satisfying the following equation:% el 4.1993 (Al _eq ) +7.4409.

In a non-limiting example, the α / β 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 α / β 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 α / β titanium alloy of the present invention exhibits the following average ductility:% el 1.1979 (Al _eq ) +8.5604.

In yet another non-limiting example, the α / β 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; average yield strength (YS) satisfying the following equation: YS 13.911 (Al _eq ) +39.435; and the unit satisfying the following equation is the average ductility of elongation% (% el):% el 1.1979 (Al _eq ) +8.5604.

It has been determined that, compared to Ti-6Al-4V alloys, non-limiting examples of the α / β titanium alloys of the present invention exhibit similar or higher mechanical strength, higher ductility, and improved formability. Therefore, it is possible to use articles formed from the alloy of the present invention as a substitute for Ti-6Al-4V alloy articles in aerospace, aviation, marine, automotive, and other applications. The high strength and ductility of the examples of the alloys of the present invention allow the manufacture to be highly resistant and currently not possible from Ti-6Al- Some rolled product shapes made of 4V alloy.

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

The following examples are intended to further describe certain non-limiting embodiments without limiting the scope of the invention. Those of ordinary skill should understand that within the scope of the present invention which is limited only by the scope of the patent application, there may be variations of the following examples, as well as other embodiments not specifically described herein.

Example 1

The conventional α / β titanium alloy ingot having the composition of the present invention is cast using conventional vacuum arc remelting (VAR), plasma arc melting (PAM), or electron beam cold chamber melting (EB), and using VAR remelting melt. The composition of the ingot is included in the range listed in the "non-limiting embodiment of the present invention" column of Table 1 above.

The aluminum equivalent value of the ingot composition produced in this Example 1 ranges from about 6.0 to about 7.1. Various hot-rolling operations are used to process the ingots into hot-rolled rods and wires with a diameter between 0.25 inches (0.635 cm) and 3.25 inches (8.255 cm). Hot rolling is performed at a starting temperature between 1550 ° F (843.3 ° C) and 1650 ° F (898.9 ° C). This temperature range is lower than the α / β transition temperature of the alloy of this example, which is 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 diameter, aluminum concentration, iron concentration, oxygen concentration, and calculated Al _eq of each rod and wire sample 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 across UTS, YS, and% el data points measured by linear regression. It can be seen that the average strength and the average elongation% both increase with the increase of Al _eq . This relationship is surprising and unexpected, as it is the opposite of the generally observed relationship of increased strength with reduced ductility.

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

Example 2

The wire samples No. 9-11 of Example 1 having a diameter of 0.5 inch (1.27 cm) and an aluminum equivalent value of about 6.5, about 6.8, and about 7.15 were subjected to a tensile test at room temperature. The results of the tensile test are shown graphically in FIG. 2. All of these samples exhibited tensile and yield strengths similar to or higher than those exhibited by commercial Ti-6Al-4V alloys. As shown in FIG. 1, it can be seen from FIG. 2 that an increase in Al _{eq results in} an increase in strength and an increase in average elongation%. As discussed above, this trend is surprising and unexpected because it is the opposite of the generally observed relationship of increased strength with reduced ductility. Compared to FIG. 1, which represents tests performed on samples of various sizes, the data in FIG. 2, which represents tests performed on samples of the same size, has a smaller spread because the mechanical properties are affected to some extent by the size of the test samples.

Example 3

A 1-inch (2.54 cm) thick plate sample was hot rolled from an ingot manufactured according to the procedure described in Example 1. The alloy ingot has a composition within the range listed in the "non-limiting embodiment of the present invention" column of Table 1 above, wherein the aluminum and oxygen concentrations and aluminum equivalent values are listed in Table 3.

All hot rolling temperatures are below the α / β transition temperature of the alloy. The alloy has an Al _eq value of 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 FIG. 3. It can be seen from FIG. 3 that, as indicated by the calculated aluminum equivalent, the strength of the alloy including increased contents of Al and O at room temperature is at least equivalent to that of the Ti-6Al-4V alloy. In addition, it was observed that the intensity increased as Al _eq increased. In addition, the average ductility of the alloy of the present invention increases slightly with the increase of Al _eq and the strength, or remains substantially unchanged. This trend is surprising and unexpected because it is the opposite of the generally observed relationship of increased strength with reduced ductility.

The invention has been described with reference to various illustrative, illustrative, and non-limiting examples. However, a person of ordinary skill should realize that various substitutions, modifications, or combinations can be made to any disclosed embodiment (or a part thereof) without departing from the scope of the present invention, and the scope of the present invention is limited only by the scope of the patent application. Therefore, it is anticipated and understood that the present invention encompasses other embodiments not explicitly set forth herein. The embodiments can be obtained, for example, by combining and / or changing any of the disclosed steps, ingredients, constituents, components, elements, features, aspects, and the like of the embodiments described herein. Therefore, the present invention is not limited by the description of various exemplary, illustrative, and non-limiting embodiments, but is limited only by the scope of patent applications. In this way, it should be understood that the scope of the patent application may be amended during the examination of the patent application of the present invention to add features to the present invention as described herein in different ways.

Claims (11)

An α / β titanium alloy, based on the total alloy weight, comprising: 4.05 to 4.40% by weight aluminum; 2.2 to 3.0% by weight vanadium; 1.24 to 1.56% by weight iron; 0.24 to 0.28% by weight oxygen; up to 0.08% by weight carbon At most 0.05% by weight nitrogen; at most 0.015% by weight hydrogen; titanium; and at most 0.30% by weight of other elements; wherein the alloy contains an aluminum equivalent of at least 6.4 and exhibits a yield strength of at least 122ksi (841.2MPa), Exhibit an ultimate tensile strength of at least 142 ksi (979.1 MPa), and exhibit a ductility of at least 20% elongation; and where the aluminum equivalent value increases to the range of 6.4 to 7.2, the average yield strength and average ultimate tensile strength Increase, and the average ductility does not decrease. An α / β titanium alloy as claimed in claim 1, wherein: these total up to 0.30% by weight of other elements include boron, tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, yttrium and cobalt At least one; when present, each of boron and yttrium is less than 0.005% by weight; and when present, each of tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese and cobalt The content is not more than 0.10% by weight. For example, the α / β titanium alloy of claim 1, wherein the aluminum equivalent value of the alloy is in the range of 6.4 to 7.2, and the yield strength is in the range of 122ksi (841.2MPa) to 155ksi (1,069MPa). For example, the α / β titanium alloy of claim 1, wherein the aluminum equivalent value of the alloy is in the range of 6.4 to 7.2, and exhibits the ultimate tensile strength in the range of 142ksi (979.1MPa) to 165ksi (1,138MPa). For example, the α / β titanium alloy of claim 1, wherein the aluminum equivalent value of the alloy is in the range of 6.4 to 7.2, and the ductility is exhibited in the range of 20% to 30% elongation. For example, the α / β titanium alloy of claim 1, wherein the aluminum equivalent value of the alloy is in the range of 6.4 to 7.2, and the yield strength in the range of 122 ksi (841.2 MPa) to 143.1 ksi (986.6 MPa) is displayed in Ultimate tensile strength in the range of 142.3 ksi (981.1 MPa) to 154.6 ksi (1,066 MPa), and exhibiting ductility in the range of 20% to 22% elongation. For example, the α / β titanium alloy of claim 1, wherein the average ultimate tensile strength (UTS) of the α / β titanium alloy in ksi meets the following equation: UTS 14.767 (Al _eq ) +48.001, standard deviation is 0.6213; where the average yield strength (YS) of the α / β titanium alloy in ksi meets the following equation: YS 13.338 (Al _eq ) +46.864; standard deviation is 0.4519; and the average ductility of the α / β titanium alloy measured in elongation% satisfies the following equation:% el 3.3669 (Al _eq ) -1.9417, standard deviation is 0.1746; where Al _eq = weight percentage of aluminum + 10 (oxygen) weight percentage. For example, the α / β titanium alloy of claim 1, wherein the average ultimate tensile strength (UTS) of the α / β titanium alloy in ksi meets the following equation: UTS 12.414 (Al _eq ) +64.429, standard deviation is 0.9576; where the average yield strength (YS) of the α / β titanium alloy in ksi meets the following equation: YS 13.585 (Al _eq ) +44.904; standard deviation is 0.8138; and the average ductility measured by the elongation percentage 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 percentage + 10 (oxygen) weight percentage. For example, the α / β titanium alloy of claim 1, wherein the average ultimate tensile strength (UTS) of the α / β titanium alloy in ksi meets the following equation: UTS 10.087 (Al _eq ) +76.785; where the average yield strength (YS) of the α / β titanium alloy in ksi meets the following equation: YS 13.911 (Al _eq ) +39.435; and wherein the average ductility of the α / β titanium alloy measured in elongation% satisfies the following equation:% el 1.1979 (Al _eq ) + 8.5604; where Al _eq = weight percentage of aluminum + 10 (oxygen) weight percentage. An article comprising an alloy as claimed in claim 1. The article of claim 10, wherein the article is 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.