US3019102A - Copper-zirconium-hafnium alloys - Google Patents

Description

Patented Jan. 30, 1962 fiicc 3,019,102 COPPER-ZIRCONIUM-HAFNIUM ALLGYS Matti J. Saarivirta, Plainfield, N.J., assignor to American Metal Climax, Inc, New York, N.Y., a corporation of New York No Drawing. Filed Aug. 19, 1960, Ser. No. 50,577 4 Claims. (Cl. 75-153) This invention relates to copper base alloys and more particularly to ternary alloys containing copper, zirconium and hafnium. The object of the invention is to provide an improved copper base alloy having superior strength and ductility properties at elevated temperatures.

Briefly stated, the alloys of the present invention are age hardenable and contain from 0.02 to 0.15% by weight of zirconium 0.1 to 1.2% hafnium, the balance being copper which is preferably initially oxygen free though any deoxidized copper may be u ed in making the alloy. With appropriate processing as will be hereafter described, the alloys are suitable as electrical and thermal conductor material useful in a variety of applications as, for example, the making of commutator segments, contactor plates and wires, welding tips and wheels, and the like.

In making the alloys of the present invention, it is essential that oxygen-free copper be used. Although any chemically deoxidized copper such as phosphorus or lithium deoxidized copper is generally satisfactory for use in making the alloy, it is preferred to use copper which is substantially oxygen free without requiring treatment with any of the conventional chemical deoxidants. Cathode copper is accordingly particularly suitable as is copper which has been produced in a reducing atmosphere such as OFHC brand copper, copper prepared in an inert atmosphere, under charcoal cover, or in a vacuum.

The alloys are made following conventional alloying practices utilizing a protective gas cover during melting of the copper, alloying and casting operations. By way of illustration, the copper is first melted under argon or other suitable protective gas cover in an alloying furnace such as an Ajax induction furnace using a graphite crucible. With the copper melt at a temperature of from 1250 to 1300 C., the alloying ingredients are added either successively or simultaneously using appropriate amounts of zirconium and hafnium in any suitable form for alloying purposes. Zirconium and hafnium as metal, sponge and master alloys of the respective metals with copper are illustrative of some of the materials that may be used in making the ternary alloys of the present invention. After alloying, the melt is held at temperature for a few minutes following which the alloy is cast into graphite or any other suitable molds. No difiiculty is experienced in producing sound castings.

Although alloys containing from 0.02 to 0.15% zirconium and from 0.1 to 1.2% hafnium, balance copper with its incidental impurities provide new and useful alloys possessing generally improved properties, it has been found that best results are obtained when the alloy contains from 0.10 to 0.15% zirconium and from 0.5 to 0.9% hafnium, balance copper.

After the casting has been prepared according to the alloying procedure as described above, the material is amendable to extensive hot working as by hot rolling, extruding or forging upon preheating the alloy to about 980 C. in a charcoal bed. Heat treatment thereof is carried out by solution annealing in a non-oxidizing atmosphere at a temperature of from about 900 to 980 C. and preferably at about 950 to 965 C. for a period of from a few minutes to about an hour depending upon the size of the casting. The solution annealed and quenched alloy may then be aged suitably at temperatures of from 300 to 600 C. and preferably between 400 and 550 C. with or without cold working of the material between the solution annealing and precipitation hardening or aging steps. In general, maximum proper ties are developed with an aging period of from one to two hours with best results being obtained by aging at from 500 to 55-0 C. when the material has not been cold worked and at temperatures of from 400 to 500 and preferably at about 450 C. when the alloy has been subjected to intermediate cold working.

Representative alloys of the present invention are listed in Table 1. The properties shown for the various alloys referred to therein were determined on unaged material after one inch diameter castings were hot rolled to 0.25 inch rods, said rods being solution annealed at 980 C. for one hour, quenched in water and then cold drawn to 0.081 inch diameter wire with reduction.

TABLE 1 Room temperature properties of Cu-Zr-Hf alloys (before s Composition Elonga- Electrical Casting Tensile Yield tion perconduco. stren th strength cent (in ti ity Percent Percent (p.s.i.) (p.s.i.) 2 inches) (percent Zr H1 I.A.O.S.

The same alloys upon being aged at 400 C. for one hour possessed the properties shown in Table 2.

TABLE 2 Room temperature propertzes 0f Cu-Zr-Hf alloys (after aging) Composition Elonga- Electrical Casting Tensile Yield tion perconduc- No. strength strengti cent (in tivity Percent Percent (p.s.i.) (p.s.i.) 2 inches) (percent The effect of varying the aging temperature on the properties of two representative alloys is shown by the 3 data in Table 3. The alloys having the composition 0.04% Zr, 0.66% Hf, balance Cu (Alloy A) and 0.11% Zr, 0.63% Hf, balance Cu (Alloy B) were processed by solution annealing at 965 C. for one hour,

quenching, cold drawing to 0.081 inch diameter wire with 90% reduction after which the material was aged as stated in Table 3.

TABLE 3 Efiect of temperature on cold worked Cu-Zr-Hf alloy wire Tensile Yield Elonga- Alloy Treatment Strength strength tion per- (p.s.i.) (p.s.i.) cent (in 2 inches) Cold worked condition 70,000 06,000 2. 4 Heated at 300 0., 1 hour 71,000 65,000 8.0 Heated at 350 0., 1 hour"..- 76, 500 68,000 11.0 Heated at 400 0., 1 hour 80,000 72,000 9.0 Heated at 450 0., 1 hour 77,000 72,000 9. Heated at 500 71,000 04, 000 0. 0 Heated at 550 1 62,000 55,000 0.0 Heated at 600 1 53,400 42,000 15.0 Heated at 650 1 42,000 21,000 28. 0 Heated at 700 1 38,500 14,000 34.0 Cold worked 00 151 71,000 63,000 4.0 Heated at 300 0 1 75, 300 69,200 9. 2 Heated at 350 0 1 78, 800 72, 000 13. 0 Heated at 400 0., 1 30, 000 73, 000 12. 0 Heated at 450 0., 1 79, 000 73, 000 8. 8 Heated at 500 0., 1 71,500 04, 400 8. 8 Heated at 550 0., 1 63,500 54,800 11.0 Heated at 600 0., 1 ,500 36,000 17. 6 Heated at 050 0., 1 hour-.. 40,500 18,000 33.0 Heated at 700 0., 1 hour 39,500 17,000 26. 0

As will be noted from Table 1, the electrical conductivity of the alloy containing 0.11% Zr, 0.63% Hf in the cold worked and unaged condition is 41% I.A.C.S. After aging for 1 hour at temperatures of 450 and 500 C., however, the electrical conductivity of the same alloy rose to values of 80 and 84% I.A.C.S. respectively.

The efiect of aging at different temperatures after solution annealing the alloy is seen from the data presented in Table 4. In these tests the alloys containing 0.04% Zr, 0.66% Hf, balance copper (Alloy A) and 0.11% Zr, 0.63% Hf, balance copper (Alloy B) were processed into 0.178 inch diameter cold drawn wire, solution annealed at 965 C. for one hour, quenched and then heated for one hour at the specified temperatures.

TABLE 4 Properties of solution annealed and aged Cu-Zr-Hf alloys Elong'a- Electrical Tensile Yield tion perconduc- Treatment strength strength cent (in tivity (p.s.i.) (p.s.i.) 2 inches) (percent ALLOY "A" S01. anneal 1 hr. at 965 C.

quench 34,000 5,600 40.0 41. 7 So]. anneal-age 1 hr. at 400 C. 35, 000 7,000 40. 0 43.0 Sol. anneal-age 1 hr. at 450 0. 33,000 7,000 40.0 44. 0 s01. anneal-age 1hr. at 500 0 33,000 8,000 43.0 43.0 Sol. anneal-age 1 hr. at 550 (1 39,000 19,000 34. 0 83. 0 Sol.anneal-age1hr.at 600 0. 35,000 15,000 35.0 82.0

ALLOY B Sol. anneal 1 hr. at 965 C.

quench 35,000 6,000 40.0 450 S01. anneal-age 1 hr. at 400 C. 35, 000 8,000 30. 0 48. 0 S01. anneal-age 1 hr. at 450 0. 38,000 8,000 38.0 47. 0 S01. anneal-age 1 hr. at 500 0. 34,000 11,000 38.0 47.0 Sol. anneal-age 1 hr. at 550 0. 41,000 20,000 40.0 86. 0 S01. anneal-age 1 hr. at 600 C. 38,000 14,000 38. 0 85. 0

It will be noted from the above data that maximum precipitation hardening occurs at 550 C. This is about 50 C. higher than other copper base alloys and indicates the superior high temperature properties of the present alloys. It will also be noted that the properties of the higher zirconium content alloy are slightly superior to the alloy containing 0.04% Zr.

The effect of variation in the extent of cold working TABLE 5 Properties of solution annealed, cold worked and aged Cu-Zr-Hf alloy Tensile Yield Elong, Elec. Treatment strength strength (percent 00nd.

(p.s.i.) (p.s.i.) in 2 (percent,

inches) LA.C.S.)

Sol. anneal 1 hr. at 965 C 35, 000 6. 000 40. 0 45. 0 Sol. anneal-age 1 hr. at 550 C. 41, 000 17,000 40.0 86. 0 S01. anneal cold work 25%.. 51, 000 48, 000 5.0 45.0 Sol. anneal cold Work 55% 62,000 59,000 3.0 44.0 Sol. anneal cold Work 67,000 63,000 3.0 44. 0 S01. anneal cold Work 71,000 63,000 4.0 41.0 Sol. anneal-cold Work 25%- age 2 hrs. at 400 C 65,000 55, 000 14.0 60. 0 S01. anneal-cold work 55%- age 2 hrs. at; 400 C 72, 000 65, 000 10. 0 08.0 Sol. anneal-cold Work 75%- age 2 hrs. at 400 C 76, 000 08, 000 12.0 68.0 Sol. anneal cold work 90%- age 2 hrs. at 400 C 80,000 72,000 12.0 66.0

The alloy of maximum tensile strength of 80,000 p.s.i. with 12% elongation and 66% electrical conductivity is obtained upon cold drawing to a reduction of 90% prior to aging the cold worked material.

The superior high temperature properties of the alloys of the present invention are made readily apparent by comparison of the high temperature tensile and elongation properties thereof with other copper base alloys such as copper-zirconium and copper-chromium which materials are generally recognized as possessing superior high temperature. tensile strength and ductility. The procedure used in making the comparison consisted of first aging the cold worked 0.081 inch diameter wire specimens of each of the alloys specified in Table 6 and allowing the specimens to cool to room temperature. The aged and cooled specimens were then reheated to 400 (2., held at this temperature for one hour and tensile strength tests were run at a crosshead speed of 0.02 inch per minute. The results are summarized in Table 6.

It will be noted that both of the tested Cu-Zr-Hf alloys not only possess superior tensile strength and elongation properties at 400 C. compared with the designated Cu- Zr, Cu-Cr and Cu-Hf alloys but also that the significant improvement with respect to such high temperature properties is not obtainable with the use of either zirconium or hafnium as the sole alloying ingredient for copper.

It is apparent that many differing embodiments of this invention may be made without departing from the spirit and scope thereof and it is not intended to be limited thereby except as indicated in the appended claims.

What is claimed is:

1. An age hardenable copper base alloy containing from 0.02 to about 0.15% zirconium, from 0.1 to about 1.2% hafnium and the remainder oxygen-free copper.

2. An age hardenable copper base alloy containing from 0.04 to about 0.15 zirconium, 0.5 to about 1% hafnium, balance oxygen-free copper, said alloy being 5 6 characterized by superior high temperature tensile strength from 0.02 to about 0.15% zirconium, 0.1 to about 1.2% and ductility in the age hardened condition. hafnium and the remainder chemically deoxidized copper 3. An homogeneous copper alloy consisting of from with incidental impurities normally associated therewith.

0.1 to 0.15% zirconium, 0.5 to 0.9% hafnium, balance References Cfied in the file of this patent copper with incidental impurities normally associated 5 therewith, said copper being oxygen-free prior to its being UNITED STATES PATENTS alloyed with said zirconium and hafnium. 2,086,329 Hensel et a1. July 6, 1937 4. An age hardenable copper-base alloy containing 2,097,816 Hensel et a1. Nov. 2, 1937

Claims (1)

1. AN AGE HARDENABLE COPPER BASE ALLOY CONTAINING FROM 0.02 TO ABOUT 0.15% ZIRCONIUM, FROM 0.1 TO ABOUT 1.2% HAFNIUM AND THE REMAINDER OXYGEN-FREE COPPER