US2938789A - Titanium-molybdenum alloys with compound formers - Google Patents

Description

United States PatentO TlTANIUM-MOLYBDENUM ALLOYS WITH COIVIPOUND FORIVIERS Robert I. Jafiee, Columbus, Ohio, assignor, by mesne assignments, to Kennecott Copper Corporation, New York, N.Y., a corporation of New York No Drawing. Filed May 18, 1959, Ser. No. 813,619

4 Claims. (Cl. 75175.5)

This invention relates to ternary and more complex alloys containing titanium and molybdenum and particularly to titanium alloys, in which molybdenum is a major alloying element, which exhibit superiormechanical and chemical properties.

This application is a continuation-in-part of copending application Serial No. 509,490, filed May 19, 1955, now abandoned.

Titanium metal and titanium alloys are light, relatively strong metals and are in great demand today as preferred materials for use in aircraft and jet engines, as well as other applications where light and strong materials are needed. There is a continual etfort to improve the mechanical and chemical properties of titanium in order to satisfy the demands for light metals with high-strength and corrosion-resistance properties.

Important strides have been taken in obtaining superior corrosion-resistance and mechanical properties by alloying titanium With molybdenum. Titanium alloys containing less than 40 percent molybdenum are well known. These alloys have excellent hardness and strength. Titanium-base alloys containing more than 45 percent molybdenum have little value commercially, in that they are difiicult to work even at elevated temperatures and thus are difiicult to produce in the wrought condition for subsequent fabrication. Titanium alloys containing less than 30 percent molybdenum are of less value, in that their strength and hardness are not as great as those containing 30 percent molybdenum or more.

The improvement of mechanical or corrosion-resistant properties is of great significance in the search for strong, light metals.

It has not been discovered that very desirable properties can be imparted to titanium-molybdenum alloys by further alloying with certain elements to form ternary and even more complex alloys.

In the titanium-molybdenum system, an increase in strength without a decrease in workability is a highly significant development.

It is, therefore, an object of this invention to improve the properties of titanium by alloying with molybdenum plus certain ternary additions and combinations thereof.

It is another object of this invention to provide complex alloys containing titanium and molybdenum that are workable and that possess high strength at both room temperature and elevated temperatures.

It is a further object of this invention to provide ternary alloys containing titanium and molybdenum that possess superior mechanical properties as compared to titanium, and titanium-molybdenum binary alloys.

It is also an object to provide alloying additions suitable for replacing molybdenum and titanium in titaniummolybdenum alloys.

- molybdenum alloys containing as much as 50 percent Other objects and advantageous features of this invention will be obvious from the following specification.

In general, this invention relates to high-strength complex alloys in which titanium and molybdenum are major constituents. Titanium-molybdenum ternary alloys containing at least one compound-forming addition selected from the group consisting of boron and silicon have been found to have superior strength to titanium and to titanium-molybdenum binary alloys with equivalent molybdenum contents. In addition, such ternary alloys have superior workability to titaniummolybdenum binary alloys at the 50 percent molybdenum level.

Titanium-molybdenum alloys containing ternary additions, selected from the group of compound-forming additions, which have limited solubilities in both alpha and beta titanium, have also been found to have superior strength properties. These ternary additions also greatly improve the workability of the titanium, SO-percentmolybdenum alloy. As has been stated, titanium alloys containing more than 45 percent molybdenum are difficult to work, even at high temperatures. Titaniummolybdenum were successfully hot-rolled or worked when small additions (up to 2 percent) of boron or silicon were made. Table I below lists the compound-forming additions and gives the preferred minimum and maximum amounts of each alloying constituent in the ternary ranges.

Table l Ternary Addition Molybdenum, Titanium,

Percent Percent Percent Element Min. Max. Min. Max. Min. Max.

Boron 0.1 1.0 30 50 50 Silicon 0. 1 2. 0 30 50 50 70 It is obvious that additions of boron and silicon can be made to ternary alloys of titanium and molybdenum for the purpose of improving their workability. In particular it has been found that high-strength titaniummolybdenum alloys consisting essentially of from 30 to 50 percent molybdenum together with up to 20 percent of a beta stabilizing metal are improved as to workability by the addition of at least one titanium compound former from the group consisting of boron and silicon in amounts from 0.1 to 2.0 percent. Well known beta stabilizers for these alloys include columbium, tantalum, tungsten, and chromium.

As can be seen in Table II the above-described alloys exhibit far. superior mechanical properties to unalloyed titanium and have a strengthening effect on the titaniummolybdenum binary alloys with equivalent molybdenum contents.

The ternary and complex alloys of the present invention are highly corrosion resistant in both acid and basic media. In an attempt to develop the grain structure of the alloys, a total of 13 acid and 2 basic etching solutions were used at a temperature of F. Also, samples were exposed to concentrated sulfuric and 25 weight percent potassium hydroxide at F. None of these etchants produced grain boundary attack.

The following table covering nearly all of the ranges disclosed above is presented to more clearly illustrate the efiects of the alloy additions of this invention.

Table II v I Vlckers Hardness Number Yield Ultimate Total Reduc- Composition, Weight Strength, Tensile Elongation 111 Bend Percent (Balance Tl) Reliability Wrought p.s.i. Strength, tion, Area, Ductility, Cast, 0.2% p.s.i. Percent Percent T Value 25 C. Ofiset Unalloyed Reliable 151 7 17s 61 20 41,500 67, 100 31 5a 0. 0

Ti-Mo ALLOYS M0 Reliable. 253 246 '186 118 52 110, 500 115, 100 13 31 1. 1 MO do 271 262 221 182 66 121, 400 121, 400 7 24 2. 2 MO --do 291 283 211 161 76 131, 600 132, 500 2 l1 3. 4 5 M0 do 331 290 208 173 84 140, 800 143, 1 11 50 0 Not Rollah1e.-- 315 328 254 221 159 -.1

Ti-Mo-B ALLOYS 30 M0, 0.1 B Rollabl'e 261 250 174 93 53 115, 800 117, 700 1.3 d 292: 274 178 110 52 123, 200' 128, 300 1. 9 269 t 278 218 156 72 125, 400 131, 100 5, 4 336 p 325 244 217 161 Brittle Fracture 18. 2

'Ii-Mo-Si ALLOYS 288' 281 111 112 as 125, 000 128; 900' 1. 3 339' 258 106 23 120, 20)- 125, 100 1. 6 321 319 256 192 78 Brittle racture 15. 6 347 365 286 244 134 22. 0

1 Pack rolled in mild steel sheath at 900 0.

I T Value-minimum satisfactory bend radius divided by the specimen thickness.

vcharacterized by high workability as compared to titanium-molybdenum binary alloys in the same molybdenum range.

3. A high-strength alloy in which titanium is a major constituent consisting essentially of from 30m -50 percent molybdenum, and from .1' to 2 percent silicon, and characterized by high workability as compared to titanium-molybdenum binary alloys in the same molybdenum range.

4. The method of improving the workability of titanium-molybdenum alloys containing molybdenum in the range from 30 to percent, comprising the step of alloying at least one compound-forming addition selected from the group consisting of boronin an amount ranging from-0.1 to 1.0 percent, and silicon in an amount ranging from 0.1 to 2.0 percent with said titanium-molybdenum alloys.

References Citedin the file of this patent UNITED, STATES PATENTS 2,614,041 Finlay Oct. 14, 1952 2,818,333 Swazy et a1. Dec. 31, 1957 2,819,960 Bomberger Jan. 14, 1958 2,821,475 Jafiee et a1. Jan. 28, 1958 2,893,864 Harris et a1. July .7, 1959 OTHER REFERENCES Transactions, AIME, April 1951, pages 335-336, article by Ogden and Jaffee.

Titanium-Silicon Alloys, Metal Treatment and Drop Forging, April 1954, pages 191-197,

Claims (1)

1. A HIGH-STRENGTH ALLOY IN WHICH TITANIUM IS A MAJOR CONSTITUENT AND CONSISTING ESSENTIALLY OF FROM ABOUT 30 TO 50 PERCENT MOLYBDENUM, FROM ABOUT 0.1 TO 2.0 PERCENT OF AT LEAST ONE TITANIUM COMPOUND-FORMING ADDITION SELECTED FROM THE GROUP CONSISTING OF BORON AND SILICON, BALANCE TITANIUM, SAID ALLOY BEING CHARACTERIZED BY SUPERIOR WORKABILITY AS COMPARED WITH THAT OF TITANIUMMOLYBDENUM ALLOYS OF COMPARABLE MOLYBDENUM CONTENT.