US3649259A

US3649259A - Titanium alloy

Info

Publication number: US3649259A
Application number: US829725A
Authority: US
Inventors: George H Heitman
Original assignee: Wyman Gordon Co
Current assignee: Wyman Gordon Co
Priority date: 1969-06-02
Filing date: 1969-06-02
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14

Abstract

This invention relates to a titanium alloy and, more particularly, to such an alloy having strength and fracture toughness, even when hot, formed by virtue of the use of aluminum, vanadium, zirconium, and cobalt.

Description

United fiates Patent Heitman 1 Mar. 14, 1972 [54] TITANIUM ALLOY 3,113,227 12/1963 Bomberger et al. ..75/i75.5

[72] inventor: George H. Heitman, Shrewsbury, Mass. FOREIGN PATENTS OR APPLICATIONS [731 Assigml wymn'cm'dm 90mm, Gram, Mass- 782,564 9/1957 Great Britain ..75/175.5 [22] Filed: June 2, 1969 810,949 3/1959 Great Britain ..75/l75.5 848,905 9/1960 Great Britain ..75/l75.5 [21] Appl. No; 829,725

Primary ExaminerCharles N. Lovell v 52 us. ca ..75/17s.5 Niamey-Norman Blodsefl [51] Int. Cl ..C22c 15/00 [58] Field ofSearch ..75/175.5; 148/32, 32.5, 133 [5 ABSTRACT This invention relates to a titanium alloy and, more particu- [56] References cued larly, to such an alloy having strength and fracture toughness, UNITED STATES PATENTS even when hot, formed by virtue of the use of aluminum,

vanadium, zirconium, and cobalt. 2,754,204 7/1956 Jaffee et al ..75/l75.5 2,868,640 1/1959 Butler ..75/ 175.5 4Claims, No Drawings TITANIUM ALLOY BACKGROUND OF THE INVENTION There has recently been considerable interest in the development of new and better high-strength, deep-hardening alloys. This has come about with the design of larger airframe and deep submergence structural parts of titanium. One deephardening alloy which is commercially available is an alloy of titanium with 13% vanadium, 11% chromium, and 3% aluminum. Another common alloy for this purpose is the one containing titanium with 6% aluminum, 4% vanadium, and 2% tin; this alloy shows high strength capability, but the strength decreases significantly in cross sections over 1 inches and above 3 inches only annealed properties are obtained. The U.S. Pat. to Butler No. 2,868,640 describes an alloy of titanium with 3-10% aluminum, 5% vanadium, l% zirconium, and 05% molybdenum; tests show that this alloy is not as strong as could be desired. Furthermore, these alloys have the disadvantage that they lose their strength when they are made into parts by hot forming methods. These and other deficiencies of the prior art alloys have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a titanium alloy having deep-hardening characteristics.

Another object of this invention is the provision of an alloy having relatively high strength in thick sections with good ductility and fracture toughness.

A further object of the present invention is the provision of an alloy system combining strength and fracture toughness (in air and in salt water) in sections up to at least 4 inch in thickness.

It is another object of the instant invention to provide alpha and beta titanium alloys of 170 to 175 Ks.i. ultimate strength range which, nevertheless, have good elevated-temperature tensile strength, and notched tensile strength.

A still further object of the invention is the provision of a titanium alloy having use as a hot-forming high-strength material, since it retains its strength after exposure to temperatures in the range from 1200 to 1300 F.

It is a further object of the invention to provide a titanium alloy system which maintains its strength after exposure to a very high temperature, so that it is useful for hot formed elements.

With the foregoing and other objects in view, which will appear as the description proceeds, the invention resides in the combination and arrangement of steps and the details of the composition hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from the spirit of the invention.

SUMMARY OF THE INVENTION In general, the invention has to do with a deep-hardening titanium alloy containing about 6% aluminum, 4 to 7% vanadium 1 to 4% cobalt, 4% zirconium, and the remainder titanium. More specifically, about 6% vanadium is used and 2 or 3% cobalt. DESCRIPTION OF THE PREFERRED EMBODI- MENT The invention consists, in the preferred embodiment, of an alloy of titanium with 6% aluminum, 6% vanadium, 2% cobalt, and 4% zirconium. Vanadium may be used in the range from 4 to 7%, and satisfactory results are obtained when the amount of cobalt lies in the range from 1 to 4%.

EXAMPLES A nominal composition was selected for evaluation in the Al-V-Co-Zr alloy system, i.e., Ti 6Al-6V-2Co-4Zr. One lbs. heat of the alloy was made. The chemical composition and beta transus temperatures are reported in Table 1.

TABLE 1 Chemical Analysis and Beta Transus Temperatures V Cc Fe C

a-i-BIB Transus TABLE II Heat treat study on titanium alloy with cobalt addition, upset forged below the beta transus 200. 1,500 F (2)AC+1,000 F AC 205 208. 1,500 F AC-i-l, 208. 212. 1,500 F (2)AC+1,150 F (4)AC 188. 193. 1,500 F.(2)AC+1,200 F.(4)AC 180. 182. 1,500" F.(2)AC+1,250 F.(4)AC 176. 181. 1.500 F.(2)WQ+1,100 F.(4)AC 206. 208. 1,300 F.(4)AO 155. 168. 1,475 F.(2)AC+1,200 F.(4)AC 160. 168. 1,475 F (2)AO+1,250 F. AC 161. 172. 1,475" F (2)AC+1,300 F )AC 150. 162. 1 500 F (2)AC+1,300 F (4)AC 167. 172. 1,450 F (2)AC+1,300 F (4)AC 161. 163.

1,500 F.(2)AC+900 F.(4)AC 225. 230.

1,500 F.(2)AC+950 F.(4)AC 225. 232. 1,350 F. 4)A 157. 160. 1,425 F.(2)AC+1,300 F.(4)AC 164. 166. 1,400 F. )AC 158. 160.5 1,475 F.(16)AC+1,250 F.(4)AC 169. 175.0 1,650 F.(2)AC+1,250 F.(4)AC 177. 188.5 1,475 F (B)AC+1,250 F (4)AC 170. 175.0 1,47 F (4)AC+1,250 F 175. 185.5 1,700 F (2)AC+1,250 F (4)AC 177. 185.0 1,600 F (2)AC+1,250 F )AC 173. 181.5 1 AC+900 F (24)AC 214. 220.0

3 In the balance of this specification, the Ti 6Al6V-2Co-4Zr will be referred to as Ti 6-6-2-4.

The ingot was received in the form of 8 inches d1 element approximately 12 inches long. The ingot was initially upset at 1,550" F. (25%) and then drawn out. The drawn billet was recrystallized at l,650 F. (above the beta transus) and from that temperature upset 25%. After the second upsetting, the forging was drawn out to 4 inches square with several wash heats of 1550 F. A section of the 4 inches square, 2-1/2 inches long was cut from the end of each heat and upset into a pancake 0.55 inches thick. The upsets were cut into tensile blanks and heat treated at various solution temperatures and aging cycles. The results of the initial heat treat study is reported in Table II.

would be helpful for hot forming operations. All of the tests taken are in the longitudinal direction and results are reported in Tables Ill through V.

While it will be apparent that the illustrated embodiments of the invention herein disclosed are well calculated adequately to fulfill the objects and advantages primarily stated, it is to be understood that the invention is susceptible to variation, modification, and change within the spirit and scope of the subjoined claims.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

l. A deep hardening titanium alloy, consisting of a. 4 to 6% aluminmn,

b. 4 to 7% vanadium, v

TAB LE I11 Tensile properties of T1 GAl-GV-ZOo-4Zr 4' square, heat treated Test remit. 0.2% as. U.T.S. EL, 3A., Location (K s.l.) (K s.l.) percent percent J Long Surface 4 Q7 m. ggg g g 1 g gig Average 166. 7 176. 13. 2 28. 1 Long center v$ R T P6. 4 112.3 e 0 33.1 I 65.0 m. .o .2

Average j 165. 7 171. s 14. o as. 0 Long mid section 41$ 500 130. o 154. s 16. o 35.1 129. 0 151. 1e. 5 35.1

Average 129. 5 15s. 0 1e. 2 as. 7 I Long mid section 4'51? 9m o ilA 2.2 .s .s

Average 86. 4 101. 1 43. 0 74. 6

From the initial heat treat results on the Ti 6624 alloy: TABLE IV Table II, two heat treatments (Test Nos. 19 and 33 in Table I1) appeared to have relatively high strength with good ductility. The two heat treatments were evaluated on fir-inch upset forging and were air cooled from the solution treating temperature. Because of the larger section size of the billet (4 inches square), the first solution treatment was followed by a water quench to allow maximum response during aging. The 4 inch square billet (approximately inches long) was solution treated at l,475 F.(2)WQ and aged 1,250" F.(4)AC. Two transverse tensiles were taken from the center of the 4 inch square 2-;6 inches from the end. The results of the two tensiles are as follows:

The results established the composition of Ti 6-6-2-4 to be a potentially deep hardenable alloy.

A section of the 4 inch square billet was cut 7 inches long and solution treated at t,600 F.(2)AC. with aging cycle of l,250 F.(4)AC. Two longitudinal bend tests were machined from the center of the 4 inch square and two longitudinal bend tests were machined from the surface. The tensile properties and fracture toughness are as follows:

Long Surface 165.8

Notched strength and fracture toughness of Ti 6Al-6V2Co4Zr, 4' square, heat treated l,600 F.(2)AC+1,260 F.(4)AC HTABLE v Stress rupture of Ti GAHlV-2Co-4Zr 4' square, heat treated 1,600" F.(2)AC+1,250 F.(4)AC "V" notch stress rupture 70 F.

K51. 180 K51. K31. 200 K 5.1. (hrs.) (his) (his) (hrs) Lonimid section 4':

are

c. l to 4% cobalt, d. 3 to 5% zirconium, and e. the remainder titanium. 2. An alloy as recited in claim 1, wherein 2% cobalt is used. 3. An alloy as recited in claim 1, wherein 4% zirconium is used.

4. An alloy as recited in claim 1, wherein 6% vanadium is used.

t t t

Claims

2. An alloy as recited in claim 1, wherein 2% cobalt is used.
3. An alloy as recited in claim 1, wherein 4% zirconium is used.
4. An alloy as recited in claim 1, wherein 6% vanadium is used.