KR102056035B1 - High strength and ductility alpha/beta titanium alloy - Google Patents

Abstract

Alpha / beta titanium alloys comprising, by weight percent, 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 a maximum of 0.30 other elements in total. Non-limiting embodiments of alpha / beta titanium alloys include aluminum equivalent values in the range 6.4 to 7.2, exhibit yield strengths in the range 120 ksi (827.4 MPa) to 155 ksi (1,069 MPa), and range 130 ksi (896.3 MPa) A maximum tensile strength of from 1 to 138 ksi (1,138 MPa) and a malleability in the range of 12 to 30 percent elongation.

Description

High Strength and Malleable Alpha / Beta Titanium Alloy {HIGH STRENGTH AND DUCTILITY ALPHA / BETA TITANIUM ALLOY}

Cross Reference to Related Applications

This application is filed on Oct. 13, 2010, and is incorporated under 35 U.S.C. from US Patent Application Serial No. 12 / 903,851, entitled “High Strength Alpha / Beta Titanium Alloy Fasteners and Fastener Stock”. US Patent Application Series No. 12 /, filed on September 23, 2010, filed September 23, 2010, entitled “High Strength Alpha / Beta Titanium Alloy Fasteners and Fastener Stock” 888,699 from 35 USC Some continuing applications claiming priority under § 120. The entire disclosures of application series numbers 12 / 903,851 and 12 / 888,699 are incorporated herein by reference.

The present application relates to high strength and ductile alpha / beta titanium alloys.

Titanium alloys typically exhibit a high strength-to-weight ratio, are corrosion resistant, and bend resistant at moderately high temperatures. For these reasons, titanium alloys are used in aerospace, aircraft, defense, marine, and automotive applications, including, for example, landing gear members, engine frames, ballistic protection, hulls, and mechanical fasteners.

Fuel savings result from weight reduction of aircraft or other moving vehicles. Thus, for example, there is a strong desire in the aerospace industry to reduce aircraft weight. Titanium and titanium alloys are attractive materials for achieving weight reduction in aircraft applications because of 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), an alpha / beta titanium alloy.

Ti-6Al-4V alloys are one of the most common titanium-based manufactured materials estimated to account for more than 50% of the total titanium-based material market. Ti-6Al-4V alloys are used in numerous applications that benefit from the advantageous combination of light weight, corrosion resistance, and high strength alloys from low to moderate temperatures. For example, Ti-6Al-4V alloys may be used in aircraft engine components, aircraft structural components, fasteners, high-performance automotive components, medical device components, sports equipment, marine applications components, and chemical processing equipment. Used to produce components.

Ti-6Al-4V alloy mill products are commonly used in mill annealed conditions or in solution treatment and aging (STA) conditions. As used herein, "mill annealed condition" refers to the state of the titanium alloy after a "mill-annealing" heat treatment, in which the product in the process is subjected to high temperatures (e.g., 1200 to 1500 F / 649-). 816 ° C.) for about 1-8 hours and cooled in stagnant air. The mill annealing heat treatment is performed after the product has been hot worked in the α + β phase region. Round bars of Ti-6Al-4V alloys having a diameter of about 2 to 4 inches (5.08 to 10.16 cm) in mill annealed conditions have a minimum specified ultimate tensile strength of 130 ksi (896 MPa) and a minimum specified yield strength of 120 ksi (827 MPa). ) At room temperature. Mill annealed Ti-6Al-4V plates are often produced according to specification AMS 4911, while mill annealed Ti-6Al-4V bars are often produced according to specification AMS 4928.

US Patent No. 5,980,655 ("'655 Patent"), which is hereby incorporated by reference in its entirety, discloses 2.90 to 5.00 aluminum, 2.00 to 3.00 vanadium, 0.40 to 2.00 iron, 0.20 to 0.30 oxygen, incidental impurities, and titanium. Disclosed is an alpha / beta titanium alloy comprising a percentage. The alpha / beta titanium alloys disclosed in the '655 patent are referred to herein as "' 655 alloys". Commercially available alloy compositions in the '655 alloy nominally include 4.00 aluminum, 2.50 vanadium, 1.50 iron, 0.25 oxygen, incidental impurities, and titanium, in weight percentages based on total alloy weight, and herein include Ti It may be referred to as -4Al-2.5V-1.5Fe-0.25O alloy.

Because of the difficulty in cold working Ti-6Al-4V alloys, the alloys are generally processed at high temperatures, generally above α ₂ Solvus temperatures (eg forging, rolling, drawing, etc.). Ti-6Al-4V alloys cannot be effectively cold worked, for example, to increase strength due to the high incidence of cracking during cold deformation (ie product failure during the process). However, it has surprisingly and unexpectedly found that the '655 alloy has a substantial degree of cold deformation / processability, as described in US Patent Application Publication No. 2004/0221929, which is hereby incorporated by reference in its entirety.

The '655 alloy can be cold worked to achieve surprisingly high strength while maintaining machinability levels of malleability. The machinability of the machinable level is defined as the condition that the alloy exhibits greater than 6% elongation. In addition, the strength of the '655 alloy is comparable to the strength achievable with Ti-6Al-4V alloys. For example, as shown in Table 6 of the '655 patent, the tensile stress measured for the Ti-6Al-4V alloy was 145.3 ksi (1,002 MPa), while the test samples of the' 655 alloy ranged from 138.7 ksi to 142.7. Tensile strength of ksi (956.3 MPa to 983.9 MPa) is shown.

Aerospace material specification 6946B (AMS 6946B) specifies a more restrictive compounding range than recited in the claims of the '655 patent. The alloy specified in AMS 6946B retains the formability of the broader element range of the '655 patent, but the minimum mechanical strength property allowed by AMS 6946B is lower than that specified for commercially available Ti-6Al-4V alloys. For example, according to AMS-4911L, the minimum tensile strength for a 0.125 inch (3.175 mm) thick Ti-6Al-4V plate is 134 ksi (923.9 MPa) and the minimum yield strength is 126 ksi (868.7 MPa). In comparison, according to AMS 6946B, the minimum tensile strength is 130 ksi (896.3 MPa) and the minimum yield strength is 115 ksi (792.9 MPa) for 0.125 inch (3.175 mm) thick Ti-4Al-2.5V-1.5Fe-0.25O plates. )to be.

If there is a continuing need for reduced fuel consumption through weight reduction of aircraft and other vehicles, improved malleable alpha / which is desirable to exhibit comparable or better mechanical properties than those shown by Ti-6Al-4V alpha / beta titanium alloys. There is a need for beta titanium alloys.

summary

According to aspects of this specification, alpha / beta titanium alloys comprise the following by weight percent 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 a maximum of 0.30 other elements in total.

According to another aspect of the present disclosure, the alpha / beta titanium alloy consists essentially of weight percent, consisting of: 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 a maximum of 0.30 other elements in total.

The features and advantages of the alloys and related methods described herein can be further understood with reference to the accompanying drawings:
1 is a plot of ultimate tensile and yield strengths as a function of aluminum equivalents for bars and wires composed of non-limiting embodiments of alloys according to the present disclosure;
FIG. 2 is a plot of ultimate tensile and yield strength as a function of aluminum equivalent for 0.5 inch (1.27 cm) diameter wire constructed of a non-limiting embodiment of an alloy according to the present disclosure; FIG.
3 is a plot of tensile strength, yield strength, and percent elongation as a function of aluminum equivalent for a 1 inch (2.54 cm) thick plate constructed of a non-limiting embodiment of an alloy according to the present disclosure.
The reader will appreciate the above details, as well as others, in light of the following detailed description of certain non-limiting embodiments of alloys and related methods in accordance with the present disclosure.

Detailed Description of Certain Non-Limiting Embodiments

In this description of the non-limiting embodiments, it is to be understood that all numbers expressing quantities or features are to be modified in all cases by the term “about”, except in the operating embodiments or otherwise indicated. Thus, unless stated to the contrary, any algebraic parameters set forth in the following description are approximate values that may vary depending on the desired properties desired in the material and by the method according to the present disclosure. At the very least, and unless an attempt is made to limit the application of the doctrine of equivalents to the scope of the claims, each algebraic parameter should be at least understood in light of the significant numbers reported and by applying conventional rounding techniques.

Any patent, publication, or other starting material referred to herein in its entirety or in part by reference does not conflict with the existing definitions, references, or other disclosure materials set forth in this disclosure. Only integrated to the extent that As such and to the extent necessary, the disclosure presented herein replaces any collision material that is incorporated by reference. Any material, or portion thereof, incorporated by reference but not conflicting with an existing definition, reference, or other disclosure material presented herein is incorporated only to the extent that there is no conflict between the integrated material and the presence disclosure material. .

Non-limiting embodiments of alpha / beta titanium alloys according to the present disclosure, in weight percent, include, consist of, or consist essentially of: 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 a maximum of 0.30 other elements in total. In certain non-limiting embodiments according to the present disclosure, other elements that may be present in the alpha / beta titanium alloy (as part of up to 0.30 weight percent of other elements) include boron, tin zirconium, molybdenum, chromium, nickel, The weight level of each such other element comprising at least one of silicon, copper, niobium, tantalum, manganese, yttrium, and cobalt, and which is present in certain non-limiting embodiments, is 0.10 or less, with two exceptions There is. The exceptions are boron and yttrium, and if they are present some other elements are present in individual concentrations of less than 0.005 weight percent.

I. Alloy Composition

Non-limiting embodiments of alloys according to the present disclosure include titanium, aluminum, vanadium, iron, and oxygen. If only alloying elements are mentioned in the compositions discussed below, the balance should be understood to include titanium and incidental impurities.

A. Aluminum

Aluminum is an alpha phase reinforcement in titanium alloys. In a non-limiting embodiment of an alpha / beta titanium alloy according to the present disclosure, the composition range of aluminum is narrower than the aluminum range disclosed in the '655 patent. In addition, the minimum level of aluminum according to certain non-limiting embodiments of the alloy according to the present disclosure is greater than the minimum level set in AMS 6946B. These compositional features have been observed to allow the alloy to exhibit more consistent mechanical properties comparable to the Ti-6Al-4V alloy. The minimum concentration of aluminum in the alpha / beta titanium alloy according to the present disclosure is 3.9 weight percent. The maximum concentration of aluminum in the alpha / beta titanium alloy according to the present disclosure is 4.5 weight percent.

B. Vanadium

Vanadium is a beta phase stabilizer in titanium alloys. The minimum concentration vanadium in the alpha / beta titanium alloy according to the present disclosure is greater than the minimum concentration disclosed in the '655 patent and set in AMS 6946B. This compositional feature was observed to provide an optimal, controlled balance of volume fractions of alpha and beta phases. The balance of alpha and beta phases provides alloys according to the present disclosure with excellent malleability and formability. Vanadium is present in the alpha / beta titanium alloy according to the present disclosure at a minimum concentration of 2.2 weight percent. The maximum concentration of vanadium in the alpha / beta titanium alloy according to the present disclosure is 3.0 weight percent.

C. Iron

Iron is a vacancy beta stabilizer in titanium alloys. Alpha / beta titanium alloys according to the present disclosure include larger minimum concentrations and a narrower range of iron as compared to the alloys described in the '655 patent. These features were observed to provide an optimal, controlled balance of the volume fractions of alpha and beta phases. Balance provides an alloy according to the present disclosure with excellent malleability and formability. Iron is present in the alpha / beta alloy according to the present disclosure at a minimum concentration of 1.2 weight percent. The maximum concentration of iron in the alpha / beta titanium alloy according to the present disclosure is 1.8 weight percent.

D. Oxygen

Oxygen is an alpha phase reinforcement in titanium alloys. The composition range of oxygen in the alpha / beta titanium alloy according to the present disclosure is narrower than the range disclosed in the '655 patent and AMS 6946B specification. In addition, in non-limiting embodiments of alloys according to the present disclosure, the minimum concentration of oxygen is greater than in the '655 patent and the AMS 6946B specification. These compositional features have been observed to allow alloys according to the present disclosure to consistently exhibit mechanical properties comparable to certain Ti-6Al-4V mechanical properties. The minimum concentration of oxygen in the alpha / beta titanium alloy according to the present disclosure is 0.24 weight percent. The maximum concentration of oxygen in the alpha / beta titanium alloy according to the present disclosure is 0.30 weight percent.

In addition to including titanium, aluminum, vanadium, iron, and oxygen as discussed above, non-limiting embodiments in alpha / beta titanium alloys according to certain disclosures do not exceed 0.30 weight percent. Contains other elements. 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, wherein 2 Exceptions, the weight percentage of each such element is 0.10 or less. The exceptions are boron and yttrium. When present in alloys according to the present disclosure, the weight percentage of each of boron and yttrium is less than 0.005.

Incidental impurities may also be present in the alpha / beta titanium alloys according to the present disclosure. For example, carbon may be present at up to about 0.008 weight percent. Nitrogen may be present at up to about 0.05 weight percent. Hydrogen may be present at up to about 0.015 weight percent. Other possible incidental impurities will be apparent to those skilled in the metallurgical art.

Table 1 provides a summary of the following compositions: (i) non-limiting embodiments in alpha / beta titanium alloys according to certain disclosures and (ii) certain alloys disclosed in the '655 patent and specified in AMS 6946B.

Table 1

The inventors have found that providing an alloy having a minimum level of aluminum, oxygen, and iron that is higher than the minimum level taught in the '655 patent provides mechanical properties such as strength, for example mill annealed Ti-6Al-4V. It has unexpectedly been found to provide alpha / beta titanium alloys that consistently exhibit mechanical properties such as strength that are at least comparable to the specific mechanical properties of the alloy. The inventors also found that an increase in the minimum level of iron and vanadium and a decrease in the range width thereof for the minimum values and ranges disclosed in the '655 patent provide alloys that exhibit optimal and controlled balance of volume fractions of alpha and beta phases in mill annealed form Unexpectedly found out. This optimal balance of phases in alpha / beta titanium alloys according to the present disclosure provides an embodiment of an alloy with improved malleability compared to Ti-6Al-4V alloys, disclosed in the '655 patent and disclosed in AMS 6946B. Maintain the malleability of the specified alloy.

Those skilled in the art understand that the strength and malleability of metal materials generally exhibit a reverse relationship. In other words, in general, as the strength of a metal material increases, the malleability of the material decreases. The combination of increased mechanical strength and retained malleability of alpha / beta titanium alloys according to the present disclosure is not expected because the inverse relationship of strength and malleability is generally observed for mill annealed titanium alloys. The unexpected and surprising combination of increased mechanical strength and retained malleability is a particularly advantageous feature of the alloy embodiments according to the present disclosure. It was surprising to observe that embodiments of alloys according to the mill annealed exhibit strengths comparable to Ti-6Al-4V alloys without showing a decrease in malleability.

Certain non-limiting embodiments of alpha / beta alloys according to the present disclosure having an aluminum equivalent value (Al _eq ) of at least 6.3, or more preferably at least 6.4, have at least a strength comparable to that of the Ti-6Al-4V alloy. Was observed. Such alloys have also been observed to have superior malleability than Ti-6Al-4V alloys, which typically have aluminum equivalent values of about 7.5. As used herein, "aluminum equivalent value" or "aluminum equivalent" (Al _eq ) means a lamp that corresponds to 10 times the aluminum concentration in weight alloy plus the oxygen concentration in the weight percent alloy. In other words, the aluminum equivalent of the alloy can be measured as follows: Al _eq = Al _(wt.%) + 10 (O _(wt.%) ).

It is recognized that the mechanical properties of the titanium alloy are generally affected by the size of the sample to be tested, but in a non-limiting embodiment according to the present disclosure, the alpha / beta titanium alloy comprises an aluminum equivalent value of at least 6.4, or In certain embodiments it is within the range of 6.4 to 7.2 and its yield strength is at least 120 ksi (827.4 MPa), or in certain embodiments at least 130 ksi (896.3 MPa).

In other non-limiting embodiments according to the present disclosure, the alpha / beta titanium alloy comprises an aluminum equivalent value of at least 6.4 or, in certain embodiments, in the range of 6.4 to 7.2, the yield strength being in the range 120 ksi (827.4 MPa). ) To 155 ksi (1,069 MPa).

In another non-limiting embodiment, an aluminum equivalent value of at least 6.4 of the alpha / beta titanium alloy according to the present disclosure, or in certain embodiments ranges from 6.4 to 7.2, the maximum tensile strength of at least 130 ksi (896.3) MPa) or in certain embodiments at least 140 ksi (965.3 MPa).

In further non-limiting embodiments according to the present disclosure, an alpha / beta titanium alloy according to the present disclosure comprises an aluminum equivalent value of at least 6.4, or in certain embodiments ranges from 6.4 to 7.2, the maximum tensile strength being in the range 130 ksi (896.3 MPa) to 165 ksi (1,138 MPa).

In further non-limiting embodiments, the alpha / beta titanium alloy according to the present disclosure comprises an aluminum equivalent value of at least 6.4, or in certain embodiments ranges from 6.4 to 7.2, the malleability of at least 12%, or at least 16% (percent tall).

In further non-limiting embodiments, the alpha / beta titanium alloy according to the present disclosure comprises an aluminum equivalent value of at least 6.4, or in certain embodiments ranges from 6.4 to 7.2, the malleability of which ranges from 12% to 30% (Percent height or "% el").

According to certain non-limiting embodiments of the present disclosure, 6.3 is an absolute minimum value of for Al _eq , but we achieve that the Al _eq value of at least 6.4 achieves the same strength as indicated by the Ti-6Al-4V alloy. It was measured that it is necessary. In another non-limiting embodiment of the alpha / beta titanium alloy according to the present disclosure, it is also noted that the maximum value of Al _eq is 7.5 and the relationship of strength to malleability according to other non-limiting embodiments disclosed herein applies. It is recognized.

According to a non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure comprises an aluminum equivalent value of at least 6.4, the yield strength of at least 120 ksi (827.4 MPa), and the maximum tensile strength of at least 130 ksi ( 896.3 MPa), and its malleable is at least 12% (height percent).

According to another non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure comprises an aluminum equivalent value of at least 6.4, the yield strength of at least 130 ksi (896.3 MPa), the maximum tensile strength of at least 140 ksi (965.3 MPa), and its malleable is at least 12%.

In another non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure comprises an aluminum equivalent value in the range 6.4 to 7.2, the yield strength of which ranges from 120 ksi (827.4 MPa) to 155 ksi (1,069 MPa). ), Its maximum tensile strength is in the range of 130 ksi (896.3 MPa) to 165 ksi (1,138 MPa), and its malleability is in the range of 12% to 30% (extension percent).

In one non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure 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 according to the present disclosure exhibits an average yield strength (YS) that satisfies the following equation:

YS ≥ 13.338 (Al _eq ) + 46.864.

In another non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure exhibits the following average malleability:

% el ≥ 3.3669 (Al _eq )-1.9417.

In another non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure represents the following:

Mean ultimate tensile strength (UTS) satisfying 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

Mean malleable to satisfy the following equation:

% el ≥ 3.3669 (Al _eq )-1.9417.

In one non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure 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 according to the present disclosure exhibits an average yield strength (YS) that satisfies the following equation:

YS ≧ 13.585 (Al _eq ) +44.904.

In another non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure exhibits the following average malleability:

% el ≧ 4.1993 (Al _eq ) + 7.4409.

In another non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure represents the following:

Mean ultimate tensile strength (UTS) satisfying the following equation:

UTS ≧ 12.414 (Al _eq ) + 64.429;

Average yield strength (YS) satisfying the following equation:

YS ≧ 13.585 (Al _eq ) + 44.904; And

Mean malleable to satisfy the following equation:

% el ≧ 4.1993 (Al _eq ) + 7.4409.

In one non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure 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 according to the present disclosure exhibits an average yield strength (YS) that satisfies the following equation:

YS ≥ 13.911 (Al _eq ) + 39.435.

In another non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure exhibits the following average malleability:

% el ≧ 1.1979 (Al _eq ) +8.5604.

In another non-limiting embodiment, the alpha / beta titanium alloy according to the present disclosure represents the following:

Mean ultimate tensile strength (UTS) satisfying 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

Average malleability of percent elongation satisfying the following equation:

% el ≧ 1.1979 (Al _eq ) +8.5604.

Non-limiting embodiments of alpha / beta titanium alloys according to the present disclosure were determined to exhibit comparable or higher mechanical strength, higher malleability, and improved formability compared to Ti-6Al-4V alloys. Thus, articles formed of alloys according to the present disclosure can be used as a substitute for Ti-6Al-4V alloy articles in aerospace, aircraft, marine, automotive, and other applications. The high strength and malleability of embodiments of the alloys according to the present disclosure have high resistance and allow the production of certain mill and finish article shapes that cannot currently be produced from Ti-6Al-4V alloys.

Aspects of the present disclosure relate to articles of manufacture comprising and / or made from alloys according to the present disclosure. Certain non-limiting embodiments of the article of manufacture can 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. . Other articles of manufacture that may be included from and / or may be made from embodiments of alpha / beta titanium alloys according to the present disclosure, now or below known to those skilled in the art, are within the scope of the embodiments disclosed herein. Those skilled in the art purchase articles of manufacture comprising and / or made from alloys according to the present disclosure by molding or other fabrication techniques known now or in the future.

The following examples are intended to further describe certain non-limiting embodiments without limiting the scope of the invention. Those skilled in the art will recognize that changes in the following examples as well as other embodiments not specifically described herein, are possible within the scope of the invention as defined only by the claims.

Example 1

An alpha / beta titanium alloy ingot having a composition according to the present disclosure is used for conventional melting using conventional vacuum arc remelting (VAR), plasma arc melting (PAM), or electron beam cold hearth melting (EB). Cast and remelted using VAR. The composition of the ingot was in the range listed in the "Non-limiting embodiment according to the present disclosure" column and includes Table 1 above.

The ingot composition produced in Example 1 has an aluminum equivalent value in the range of about 6.0 to about 7.1. Ingots were processed into hot rolled bars and wires having a diameter of 0.25 inches (0.635 cm) and 3.25 inches (8.255 cm) using various hot rolling runs. Hot rolling was performed at start temperatures of 1550 ° F. (843.3 ° C.) and 1650 ° F. (898.9 ° C.). This temperature range is below the alpha / beta 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 chemistry. After hot rolling, the hot rolled bars and wires were annealed at 1275 ° F. (690.6 ° C.) for 1 hour and then air cooled. The diameter, aluminum concentration, iron concentration, oxygen concentration, and calculated Al _eq of each bar and wire samples produced in Example 1 are provided in Table 2.

1 graphically displays room temperature ultimate tensile strength (UTS), yield strength (YS), and percent elongation (% el) for wire samples and as listed in Table 2 as a function of the aluminum equivalent value of the alloy in the sample. . 1 also includes trend lines through the UTS, YS, and% el data points measured by linear regression. It can be seen that both mean intensity and mean percent elongation increase with increasing Al _eq . This relationship is surprising and unexpected as opposed to the generally observed relationship that increased strength is accompanied by reduced malleability.

Typical Ti-6Al-4V minimums for UTS and YS are 135 ksi (930.8 MPa) and 125 ksi (861.8 MPa), respectively. The YS for the samples of the invention listed in Table 2 ranged from about 125 ksi for samples with Al _eq about 6.0 and up to about 141 ksi for samples with Al _eq about 7.1. The sample with Al _eq about 6.4 exhibited an YS of about 130 ksi (896.3 MPa). UTSs for the samples of the invention listed in Table 2 ranged from about 135 ksi for samples with Al _eq about 6.0 and up to about 153 ksi for samples with Al _eq about 7.1. The sample with Al _eq about 6.4 exhibited an YS of about 41 ksi (972 MPa).

Example 2

Tensile tests were made at room temperature for wire sample Nos. 9-11 of Example 1 having a diameter of 0.5 inches (1.27 cm) and aluminum equivalent values of about 6.5, about 6.8, and about 7.15. The results of the tensile test are shown graphically in FIG. All these samples exhibited tensile strength and yield strength comparable or greater than the strength seen by commercial Ti-6Al-4V alloys. As shown in FIG. 1, it can be seen from FIG. 2 that the intensity increases with increasing Al _eq and the average percent elongation also increases. As discussed above, this trend is surprisingly unexpected because the increase in strength is contrary to the generally observed relationship that is accompanied by a decrease in malleability. Less scatter in the representative FIG. 2 data of trials performed on samples of the same size as compared to FIG. 1, representative of the tests performed on samples of various sizes, indicates that the mechanical properties are dependent on the size of the test sample. This is because it is somewhat affected.

Example 3

Hot rolled 1 inch (2.54 cm) thick plate samples were made from ingots prepared according to the steps described in Example 1. The alloy ingot had the compositions in the ranges listed in the "Non-limiting Embodiments According to the Present Disclosure" column of Table 1 above, with the aluminum and oxygen concentrations and aluminum equivalent values listed in Table 3.

All hot rolling temperatures were below the alpha / beta transition temperature of the alloy. The alloy had an Al _eq value of about 6.5 to about 7.1. The room temperature tensile test was used to measure tensile strength, yield strength, and percent elongation (allelicity). The results of the tensile test are shown graphically in FIG. 3. It can be seen from FIG. 3 that the alloy comprising increasing levels of Al and O, as indicated by the calculated aluminum equivalents, exhibited room temperature strength at least comparable to that shown by the Ti-6Al-4V alloy. Moreover, the strength was observed to increase with increasing Al _eq . In addition, the average malleability of the alloy of the present invention remains slightly increased or generally unchanged with increasing Al _{eq and} increasing strength. This tendency is surprising and unexpected, as the increase in strength is in contrast to the generally observed relationship that is accompanied by a decrease in malleability.

The present disclosure has been written with reference to various illustrative, illustrative, and non-limiting embodiments. However, one of ordinary skill in the art appreciates that various substitutions, modifications, or combinations of any disclosed embodiments (or portions thereof) may be made without departing from the scope of the invention as defined by the claims. Will be. Accordingly, the present disclosure is to be considered and understood to encompass additional embodiments that are not explicitly set forth herein. Such embodiments can be obtained, for example, by combining and / or modifying any of the disclosed steps, components, components, components, elements, features, aspects, etc. of the embodiments described herein. Thus, the present disclosure is not limited by the description of the various illustrative, illustrative, and non-limiting embodiments, but rather by the claims only. In this way, it will be understood that the claims may be amended during the prosecution of this patent application to add features to the claimed invention as variously described herein.

Claims (28)

A method for producing a titanium alloy fastener stock, the method comprising:
Providing an alpha / beta titanium alloy comprising the following weight percent 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;
0.015 hydrogen max,
At most 0.30 other elements, wherein at most 0.30 other elements are each less than 0.005 boron and yttrium, and tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, and cobalt less than 0.15 each Including, and
Balance titanium and incidental impurities;
Hot rolling the titanium alloy below the alpha / beta transition temperature of the titanium alloy;
Annealing the titanium alloy at an annealing temperature in the range of 1,200 ° F. (648.9 ° C.) to 1,500 ° F. (816 ° C.) for an annealing time in the range of 1 hour to 8 hours;
Air cooling the titanium alloy; And
Machining the titanium alloy to a predetermined size;
Herein, when the aluminum equivalent value is increased in the range of 6.4 to 7.2, the average yield strength and the average maximum tensile strength of the titanium alloy increase but the average malleability does not decrease.
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