US2864698A - Titanium base aluminum-tantalumcolumbium alloys - Google Patents

Description

United States Patent TITANIUM BASE ALUMINUM-TANTALUM- COLUMBIUM ALLOYS Stanley Ahkowitz and Paul E. Moorhead, Warren, Ohio, assignors to Mallory-Sharon Titanium Corporation, Niles, Ohio, a corporation of Delaware Application June 19, 1956, Serial No. 592,277

5 Claims. (Cl. 75175.5)

The invention relates to titanium base alloys and more particularly to quaternary titanium base alloys containing aluminum, tantalum and columbium. More particularly the invention relates to a titanium sheet alloy which is Weldable and has a minimum yield strength as annealed of 110,000 p. s. i. with satisfactory ductility.

Ever since the advent of the use of titanium and titanium alloys in the manufacture of parts for airplanes, airplane engines and other articles where high strength, corrosion resistance and minimum weight are important factors, there has been a problem in providing titanium alloy material and particularly sheet material which combines weldability with high strength at room temperature as well as at elevated temperatures.

Certain prior'aluminum-Vanadium-titanium alloys have favorable high temperature properties and can be fabricated readily but they are not readily Weldable particularly in sheet material. Certain prior aluminum-tintitanium alloys are Weldable and may be formed but are ditlicult to manufacture in sheet form and they do not have the room temperature and high temperature strength below 1000 F. of the aluminum-vanadium-titanium alloys.

In other words, for certain applications it has been necessary to sacrifice strength and use lower strength material in order to have a material which is weldable.

We have discovered that certain quaternary alloys of titanium, alumintnn, tantalum and columbium approach the high temperature properties and ease of fabricability of prior aluminum-vanadium-titanium alloys such-as a 6 Al-4 V titanium alloy while maintaining the formability and weldability of certain prior aluminum-tin-titanium alloys such as 5 Al-2.S Sn titanium alloys.

The alloys of the present invention have a 10,000 p. s. i. better room temperature yield strength, with this advantage stillmaintained at 1000 F., than prior aluminum-tin-titaniurn alloys. That is to say, alloys of the present invention have a 120,000 p. s. i. minimum yield strength at room temperature and a 67,000 p. s. i. minimum yield strength at 1000 F. with comparable bend and tensile ductility and better impact strength than prior aluminum-tin-titanium alloys.

At the same time, the improved alloys of the present invention have weldability comparable to the prior aluminum-tin alloy.

Finally, the improved alloys of the present invention can be forged or rolled and sheet material can be manufactured therefrom .with less difficulty than the considerable difficulty heretofore experienced in rolling titanium alloys which are weldable.

Finally, the cost of the improved alloys of the present invention from the standpoint of material costs is not appreciably in excess of the cost of other titanium alloys in use.

Accordingly, it is an object of the present invention to provide a new quaternary titanium sheet alloy characterized by having a desirable and heretofore unobtainable 2,864,698 Patented Dec. 16, 1958 ice 2 combination of weldability and high strength together with ease of fabricability and ready formability.

Moreover, it is an object of the present invention to provide a new quaternary titanium alloy having for one analysis, a 120,000 p. s. i. minimum yield strength at room temperature and a 67,000 p. s. i. yield strength at 1000 F., and having bend and tensile ductility prop erties and impact strength comparable to or better than weldable titanium alloys heretofore available.

Also, it is an object of the present invention to provide a new quaternary titanium alloy which is Weldable and which has high temperature strength properties comparable to titanium alloys heretofore available which were not weldable.

Furthermore, it is an object of the present invention to provide a new quaternary titanium alloy having the indicated weldability and strength properties and which has formability required for the fabrication of sheet metal parts therefrom.

Also, it is an object of the present invention to provide a new quaternary titanium sheet alloy which can be easily fabricated by rolling or forging to semi-finished or finished form such as to produce bars or sheets.

Also, it is an object of the present invention to provide a new quaternary titanium sheet alloy which approaches the high temperature properties and ease of fabricability of the known 6 Al-4 V titanium alloy while maintaining the formability and weldability of the 5 Al-2.5 Sn titanium alloy.

In addition, it is an object of the present invention to provide a new quaternary titanium alloy combining the indicated characteristics and properties without substantially increasing the cost thereof due to the addition of the special alloying elementsused.

Finally, it is an object of the present invention to provide a new quaternary titanium base alloy containing from 5% to 9% aluminum, from 33% to 3.33% tantalum, from 33% to 3.33% columbium, and the balance substantially titanium.

These and other objects and advantages apparent to those skilled in the art from the following description and claims maybe obtained, the stated results achieved, and the described difficulties overcome by the discoveries, principles, compositions and alloys which comprise the present invention, the nature of which is set forth belowillustrative of the best modes in Which applicants have contemplated applying the principles-and which are particularly and distinctly pointed out and set forth in the appended claims forming part hereof.

The alloys of the present invention may be prepared from either commercial titanium or high purity titanium. Where prepared fromcommercial titanium, a typical analysis of the material, in addition to titanium, aluminum, tantalum and columbium, is 0.02% C, 0.01% N 0.10% 0 and 0.005% H However, the invention is not restricted to the use of material having the typical interstitial level indicated, as the level may be of the order of 0.06% C, 0.03% N 0.15% 0 and 0.02% to 0.024% H In other words, presently available sponge having a sponge hardness of 120 BHN is suitable. The sponge hardness may range from BHN to 150 BHN. in examples given below, titanium sponge having a typical interstitial level of BHN was used.

In practice, the titanium is preferably melted by the electric arc process in a Water-cooled copper crucible in an atmosphere such as argon and the alloy elements are added to the melt either by the addition of aluminum and alloys of tantalum and columbium or by the addition of 'an alloy of aluminum, tantalum and columbium.

In general, the alloys of the present invention comprise from 5% to 9% aluminum, and from 1% to 5% a combination of tantalum and columbium. The tantalum and columbium content may be in the ratio of from 2 tantalum to 1 columbium to a ratio of l tantalum to 2 columbium. More particularly, preferred alloys of the present invention may comprise 7% aluminum, and 5% tantalum and columbium or 8% aluminum and 3% tantalum and columbium, preferably in the range of ratios between 1 to 2 or 2 to 1 tantalum and columbium.

The alloys of the present invention after melting and casting may be processed in the usual manner and forged or rolled to form the desired semi-finished or finished product. For instance, ingots of the improved quaternary alloys may be forged or bloomed to slab form, hot rolled to sheet bar, and the sheet bar may be rolled to form finished sheets, say, .020 to .090" thick.

Several examples of the improved alloy of the present invention are as follows:

Table I Nominal or Intended Composition Example No.

Percent Percent Percent Percent A1 Ta Cb T1 Bal. Bal. Bal.

The mechanical properties of sheets fabricated from alloys of the present invention as determined by evaluation, are indicated in Table II below:

Table II [As-annealed at 1700 F.% hr.; furnace cooled to 1100 F.Air cooled] The various properties of the improved alloys of the invention indicated in the tables are illustrated in the drawing in which Figure 1 illustrates yield strength and ultimate strength, Figure 2 illustrates elongation, Fig- -ure 3 illustrates bend values and Figure 4 illustrates weldability. The points in the graphs in each of Figures 1, 2, 3 and 4 are for alloys having 1%, 3% and 5% a combination of tantalum and columbium, with a ratio of about one part tantalum and two parts columbium, 7% aluminum, and the balance substantially titanium.

The graphs of Figures 1 and 2 show that an alloy with 1% combined tantalum and columbium give good ductility and that as increasing amounts of combined'tantalum and columbium are added, the strength is increased and the ductility lowered and with good ductility where the combined tantalum and columbium is 5%.

The bend graph of Figure 3 shows good formability for the material over the entire range and with little change over the entire range of from 1% to 5% combined tantalum and columbium.

Referring to the elongation graph of Figure 4, compared with the elongation graph of Figure 2, the value only dropped to a 9% elongation value after heating to 2000 F. for three minutes and air cooling. These are the conditions encountered during welding. Such an elongation value, which as noted in Figure 4 is substantially the same regardless of the combined tantalum and columbium content over the 1% to 5% range, is considered very good ductility for a welded joint. Further, Figure 4 shows that the bend value is substantially unaffected by welding, when the graph of Figure 4 is considered with that of Figure 3.

Thus, the addition of 1% or more combined tantalum and columbium substantially improves the ductility of a titanium aluminum alloy, which is a characteristic very much to be desired, as high aluminum titanium alloys in the range, say, of 6% to 8% aluminum normally are embrittled by the aluminum content thereof.

To summarize, the alloys of the present invention are characterized by good formability, good ductility, high strength at room temperature and elevated temperatures, weldability and ease of manufacture.

An alloy of aluminum tantalum and columbium has a lower melting point than the melting point of either tantalum or columbium alone. This characteristic facilitates melting and alloying of an aluminum-tantalumcolumbium alloy with titanium and in producing a homogeneous product without segregation of tantalum or columbium in the melt. Such segregation, if present, could. embrittle the material. Further the cost of the aluminum-tantalum-columbium alloy used is substantially less than the cost of an equivalent amount of these elements if used in the pure form.

Although the alloys of the present invention have been described particularly as sheet alloys, the use of the same is not limited to the manufacture of sheet material as the desirable properties can be availed of in other kinds of semi-finished or finished titanium alloy products, such as bars.

It is to be understood that in the foregoing tables, where intended composition is indicated, there may be some variation in actual composition determined by chemical analyses. Compositions usually are close to the nominal or intended composition but may vary slightly either way from the intended values, depending upon the ability to control the exact amount of alloying additions made. Also where percentages are given, percent by weight is intended.

When weldability is referred to herein, the use of such term is intended to indicate that the material can be joined by welding without embrittlement of the material in and adjacent the welded joint.

Other characteristics of the new alloys of the present invention are that the improved quaternary titanium base aluminum-rantalum-columbium alloys surpass the elevated temperature strength of prior 6 Al-4 V alloys at 1000 F. Further, the strength of the improved alloys of the present invention at room temperature may be increased by the addition of larger amounts of aluminum or of: combined tantalum and columbium while the strength at elevated temperatures may be increased by the addition of greater amounts of aluminum.

The alloys of the present invention accordingly provide quaternary titanium alloys which are easier to make than other weldable alloys, which have high temperature properties and ease of fabricability of one known prior titanium alloy, along with the formability and weldability of another known titanium alloy, which combination of properties heretofore was not obtainable in any known titanium alloy.

In the foregoing description certain terms have been used for brevity, clearness and understanding, but no unnecessary limitations are to be implied therefrom be yond the requirements of the prior art, because such terms are used for descriptive purposes herein and are intended to be broadly construed.

Having now described the invention, the features, discoveries and principles thereof, the characteristics of the new alloys, several examples of preferred embodiments of the new alloys, and the new and useful results obtained; the new and useful compositions, combinations, products, discoveries and principles, and reasonable mechanical equivalents thereof obvious to those skilled in the art are set forth in the appended claims.

We claim:

1. A weld-able titanium base alloy consisting of 5% to 9% aluminum, 33% to 3.33% tantalum, 33% to 3.33%

columbium, and the balance titanium with incidental impurities.

2. A weldable titanium base alloy consisting of 5% to 9% aluminum, 1% to 5% combined tantalum and columbium in the range of ratios between 1 to 2 and 2 to 1 tantalum and columbium and the balance titanium with incidental impurities.

3. A weldable titanium base alloy consisting of 7% aluminum, 1.7% tantalum, 3.4% columbium, the balance titanium with incidental impurities; and said alloy 10 having as-annealed, a yield strength of 124,400 p. s. i. and elongation of 12.7%.

4. A weldable titanium base alloy consisting of 7% aluminum, 1% tantalum, 2% columbium, the balance titanium with incidental impurities; and said alloy having as-annealed, a yield strength of 110,000 p. s. i. and elongation of 15.7%.

5. A weldable titanium base alloy consisting of 7% aluminum, .3% tantalum, .7% columbium, the balance titanium with incidental impurities; and said alloy having as-annealed, a yield strength of 100,800 p. s. i. and elongation of 18.1%.

References Cited in the file of this patent UNITED STATES PATENTS 2,754,204 Iafl'ee et a1. July 10, 1956

Claims (1)

1. A WELDABLE TITANIUM BASE ALLOY CONSISTING OF 5% TO 9% ALUMINUM, .33% TO 3.33% TAMTALUM, .33% TO 3.33% COLUMBIUM, AND THE BALANCE TITANIUM WITH INCIDENTAL IMPURITIES.

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