US3841921A

US3841921A - Process for treating copper alloys to improve creep resistance

Info

Publication number: US3841921A
Application number: US00337310A
Authority: US
Inventors: E Shapiro; J Crane
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1973-03-02
Filing date: 1973-03-02
Publication date: 1974-10-15
Anticipated expiration: 1991-10-15

Abstract

Improving the creep resistance and stress relaxation resistance of copper base alloys having a low stacking fault energy by cold working from about 10 to 90 percent; heating from about 25* to 360*C and cooling to room temperature.

Description

Shapiro et a1. 1

PROCESS FOR TREATING COPPER ALLOYS TO IMPROVE CREEP RESISTANCE Inventors: Eugene Shapiro, l-lamden; Jacob Crane, Woodbridge, both of Conn.

Olin Corporation, New Haven, Conn.

Filed: Mar. 2, 1973 Appl. No.: 337,310

Assignee:

References Cited UNITED STATES PATENTS 12/1944 Morris 148/11.5

4/1954 Gregory 1 148/11.5 R 8/1957 Gregory 148/1l.5 R

[ -Oct. 15, 1974 3,046,166 7/1962 Hartmann l48/ll.5 3,287,180 11/1966 Eichelman et al. 148/1 1.5 R

3,297,497 1/1967 Eichelman et a1 148/12.7 3,399,084 8/1968 Eichelman et al.. 148/1 1.5 R 3,464,865 9/1969 Eichelman 148/11.5 3,753,696 8/1973 Shibata et a1. l48/l2.7

OTHER PUBLICATIONS Sacas, G., et a1.; Practical Metallurgy, Cleveland (ASM), 1940, pp- 138-146, [TN665 S240].

Barrett, C., et al.; Structure of Metals, New York, 1966, (3rd Ed.) pp. 390-393, 451-453 & 462-465, E S-29. 3.L

Primary ExaminerWa1ter R. Satterfield Attorney, Agent, or Firm-Robert H. Bachman [57] ABSTRACT lmproving the creep resistance and stress relaxation resistance of copper base alloys having a low stacking fault energy by cold working from about 10 to 90 percent; heating from about 25 to 360C and cooling to room temperature.

19 Claims, No Drawings PROCESS FOR TREATING COPPER ALLOYS TO IMPROVE CREEP RESISTANCE BACKGROUND OF THE INVENTION This invention relates to a process for improving the creep resistance and the stress relaxation resistance of copper base alloys having a low stacking fault energy. It is a desirable objective to be able to process copper base alloys in such a manner so as to provide suitable spring properties for use in electrical connectors and like components. The properties of the materials which are required for obtaining suitable performance in electrical contactors or connectors are diverse. Aside from stress corrosion and electrical conductivity requirements specifically applicable to most parts of this type, they also require that either good contact be maintained during service or that a given stress produce a given deflection. In most of these parts the load is cycled, and as a consequence on reloading the previously mentioned requirements must still be met. I

It is known that materials can exhibit a time dependent strain under a stress that is below the yield strength as determined by engineering methods or if rcstrained may undergo a reduction stress. The former characteristic is called creep and the latter characteristic is referred to as stress relaxation. In spring loaded parts, it is thus a desirable feature of an alloy that it exhibit high creep resistance and high stress relaxation resistance under the highest desirable loads possible.

SUMMARY OF THE INVENTION is applicable contain as a first element a metal from the.

group consisting of about 2 to 12 percent aluminum, about 2 to 6 percent germanium, about 2 to 10 percent gallium, about 3 to 12 percentindium, about I to 5 percent silicon, about 4 to 12 percent tin, about 8 to 37 percent zinc and the balance essentially copper. The

alloy may further include other additions such as, for example, a second element different from the first element and selected from the group consisting of about 0.001 -to 10 percent aluminum, about 0.001 to4 per cent germanium, about 0.001 to 8 percent gallium, about 0.001 to 10 percent indium, about 0.001 to 4 percent silicon, about 0.001 to 10 percent tin, about 0.001 to 37 percent zinc, about 0.001 to percent nickel, about 0.001 to 0.4 percent phosphorus, about 0.001 to 5 percent iron, about 0.001 to 5 percent cobalt, about 0.001 to 5 percent zirconium, about 0.001 to 10 percent manganese and mixtures thereof. Preferred ranges for these various elements are specified in the detailed description.

The alloys thus provided havea low stacking fault energy generally less than ergs per square centimeter. In accordance with this invention, the alloys are cold worked from about 10 to 97 percent and then heated to a temperature of from about 200 to 360C, followed by cooling to room temperature. The alloys as thus treated have improved resistance to creep and resistance to stress relaxation.

In accordance with another embodiment of this invention, intermediate cold working and annealing steps may be interposed before the aforenoted cold rolling and heating step.

Accordingly, it is an object of this invention to provide a process for improving the creep resistance and the stress relaxation resistance of copper base alloys having a low stacking fault energy.

It is a further object of this invention to provide a process as above including a low temperature thermal treatment which provides said improvements.

Other objects and advantages will become apparent to those skilled in the art from the ensuing detailed description.

DETAILED DESCRIPTION OF. THE PREFERRED EMBODIMENTS In accordance with the process of this invention, an alloy consisting essentially of a first element selected from the group consisting of about 2 to 12 percent aluminum, about 2 to 6 percent germanium, about 2 to 10 percent gallium, about 3 to 12 percent indium, about 1 to 5 percent silicon, about 4 to 12 percent tin, about 8 .to 37 percent zinc, and the balance essentially copper is provided. The alloy thus provided is cold worked from about 10 to 97 percent, and preferably from about 15 to 95 percent, and is then subjected to a low temperature thermal treatment which comprises heating the alloy to a temperature offrom about 200 to 360C, and preferably from about 220 to 350C, followed by cooling to room temperature. The heat up and cool down rates for the low temperature thermal treatment are not a critical aspect of this invention, and conventional practices may be followed; Preferably, for the low temperature thermal treatment the alloy is held at temperature for at least one minute and most preferably for at least 15 minutes.

The alloy to which the process of this invention is applied may include further elements as additions. For example, the alloy may include at least one second element different from the first element, the second element being selected from the group consisting of about 0.001 to 10 percent aluminum, about 0.001 to 4 percent germanium, about 0.001 to 8 percent gallium, about 0.001 to 10 percent indium, about 0.001 to 4 percent silicon, about 0.001 to 10 percent tin, about 0.001 to 37 percent zinc, about 0.001 to 25 percent nickel, about 0.001 to 0.4 percent phosphorus, about 0.001 to 5 percent iron, about 0.001 to 5 percent cobalt, about 0.001 to 5 percent zirconium, about 0.001 to 10 percent manganese, and mixtures thereof.

With respect to the second element or elements, the use of aluminum, silicon, tin or zinc is effective to reduce the stacking fault energy of the alloy. Nickel, iron,

I cobalt, zirconium and manganese are effective to regroup consisting of about 2 to 10 percent aluminum,

about 3 to 5 percent germanium, about 3 to 8 percent gallium, about 4 to 10 percent indium, about 1.5 to 4 percent silicon, about 4 to 10 percent tin, and about 15 to 37 percent zinc.

The second element is preferably selected from the group consisting of about 0.01 to 4 percent aluminum,

I The invention will specific examples.

, j 3 about 0.01 to 3 percent germanium, about 0.0l to 7 percent gallium, about 0.01 to 9 percent indium, about 0.0l to 3.5 percent silicon, about 0.01 to 8 percent tin,

' about 0.01 to 35 percent zinc, about 0.01 to 20 percent nickel, about 0.01 to 0.35 percent phosphorus, about 0.01 to 3.5 percent iron, about 0.01 to 2 percent cobalt, about 0.01 to 3.5 percent zirconium, about 0.01 to 8.5 percent manganese.

'The' alloys treated in accordance with this invention Pfi i flfllf astaslsisaiaa temanatesthan 10 s v Table icon, 0.27 to 0.42 percentcobalt, balancecopper) pro-' cessed to a 0.003 millimeter grain size, cold rolled approximately 50 percent with and without a final low temperature thermal treatment in accordance with this invention.

For the creep tests the stress was 50 percent of the 0.2 percent yield stress and the temperature was 125C. For the stress relaxation tests the stress was 90 percent of the 0.2 percent yield stress. The results of the test are ,ergs per square centimeter.

In accordance with another embodiment of this invention, one or more series of cold working and intermediate annealing steps may be employed prior to the cold working and low temperature thermal treatment set out above. In this embodiment, the alloys are provided as in accordance with the previous embodiment and are then cold worked from about 10 to 97 percent and preferably. from about to 95 percent, followed by intermediate annealing for'at least one'minute at a temperature of from about300 to 750C so: as to recrystallize thealloys, and preferably from about 350 to 700C. This intermediate series of cold working and annealing steps may be repeated as desired to obtain the desired gage and temperin the final material.

The data in Table I show that the low temperature thermal treatment of this invention improves the creep resistance and the stress relaxation resistanceof the alloy. Low temperature thermal treatments from about 225 to about 350C were shown to produce similar improvements in creep and stress relaxation resistance performance without significantly degrading tensile properties. i

EXAMPLE ll Table II shows creep strain versus time and percent stress relaxation versus time for CDA Alloy 638 processed to a range of grain sizes, cold rolled to I 3 percent with and without a final low temperature ther- Following the intermediate annealing step, the alloy 4 is processed as in the previous-embodiment, namely, it

mal treatmentin accordance with this invention. Test conditions were essentially the same as those of Example I.

TABLE II Stress Relaxation Test Creep Tests, Strain Rela ion Grain Thermal Stress, Stress,

Size Treatment ksi I00 hr 1000 hr ksi 24 hr 1000 hr MM 0C 0.003 None 56 0.l 0.245 88.9- I 7.24 l2.3 0.003 310 55.5 0.06 0.125 97.65 t 1.72 3.2 0.007 None 55.5 0.150 0.23 0.007 53 0.038 0.080 1.04 2.3

bly from about 15 to percent, and then heated to a temperature of from about 200 to 360C, and preferably from about 220 to 350C, followed by cooling to room temperature.

As the alloys are formed into desired-articles following the low temperature thermal treatment of this invention, it may be necessary to repeat the low temperature thermal treatment following the forming operation in order to obtain the desired creep and stress relaxation properties. Strip which is to be extremely de-- formed to produce a final article may require either the final thermal treatment be provided before'and after fabricating the article or just'after fabrication.

EXAMPLE I EXAMPLE l-ll Table III below shows that grain coarsening and the heat treatments in accordance with this invention do now be illustrated by reference to t Table l below shows creep strain versus time for V .CDAitllexttZ-S Pst ntalvm nsnt .1? pstqs usi r not adversely affect the conventional. engineering strength of the alloy of the previous example.

' TABLE lll Alloy Grain Size 9! CR Treatment UTS/O.2YS/% E .638 0.003 mm so None l25.9lll 1/5 638 0.003 mm so 310%: l27Il09/ND 638 0.007 mm so None 117110513 638 so 0.007 mm 3l0C ll7/l06/3 EXAMPLE iv A sample of cold rolled CDA Alloy 638 having a composition similar to that of Example I with a yield strength of about 81 to 95 ksi was fabricated into an electrical receptacle. In order to determine if the receptacle so formed performed acceptably, it was subjected to the following test: An oversize plug was first inserted into the receptacle and then removed. Then an undersize plug with a suitable weight hanging from it was inserted into the receptacle. The test requirements are that the weighted undersize plug must not fall out, Le, a given contact pressure must be maintained between the receptacle and the prongs of the plug. A conventional cold rolled and formed CDA Alloy 638 part could not meet this test requirement. When the parts were given thermal treatments in accordance with this invention and submitted to the same test procedures the results obtained showed that the untreated material failed in multiple specimens; whereas, material treated from 280C to 345C passed in 18 out of 20 specimens.

The results indicated that low temperature thermal treatments in accordance with this invention increase the residual contact pressure after cycling with an oversize plug so that the undersize plug does not fall out. The results also indicate that optimum performance is dependent on the heat treatment temperature.

EXAMPLE V 6 mally treated strip in accordance with this invention into a desired article, followed by a repetition of the low temperature thermal treatment in accordance with this invention.

EXAMPLE Vl Commercially produced CDA Alloy 510 was tested in two conditions (as cold rolled 54 percent and as cold rolled plus a low temperature thermal treatment in accordance with this invention at 220C). The tests were carried out at 125C and a stress equal to one-half the 0.2 percent offset yield stress at room temperature. The results are shown in Table V.

TABLE V fiP l@. Condition Test Stress. ksi 100 hrs 1000 hrs untreated 51 0.080 0.155 treated 47 0.021 0.063

' stress relaxation resistance of a wide variety of copper base alloys having low stacking fault energy. The examples also illustrate that increasing or coarsening the grain size of the respective alloys is also effective for improving the aforenoted properties.

Therefore, it is possible in accordance with this inve ntion to provide a step in the process for coarsening TABLE lV Alloy Condition Relaxation in 5 minutes 638, 0.003 mm CR 30% 310C/1 hr 1.4 638. 0.003 mm CR 30% 310C/1 hr 2%% strain 1.8 638. 0.003 mm CR 30% 310C/l hr 10% strain 2.7 638. 0.003 mm CR 30% 310C/1 hr 10% strain 310C/l hr 1.5 638. 0.007 mm CR 310C/l hr 1.6- 638, 0.007 mm CR 40% 310C/1 hr 2%% strain 2.0 638, 0.007 mm CR 40% 310C/l hr 10% strain 3.1 638, 0.007 mm CR 40% 310C/1 hr +10% strain 310C/1 hr 90.000 psi initinl stress in each case.

the grain size of the alloy to at least 0.006 mm, as, for example, by a process similar to that set out in U.S. application Ser. No. 309,345, now U.S. Pat. No. 3,788,902. filed Nov. 24, 1972, by the instant inventors. In accordance with that application. alloys having a composition similar to CDA Alloy 638 are subjected to grain coarsening by subjecting them to a cold reduci aapsiansealrith' ..P@q fiqranss 9f ed ctio and.

carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment'is therefore to be considered as in all respects illustrative and not restrictive, thescope of the invention being indicated by the appended claims, and all changes which come within the meaning and'range of equivalency are intended to be embraced therein.

What is claimed is: A 1 LA process 'for. improving the creep resistance and the stress relaxation resistance of copper base alloys having low stacking faulten'ergy without significantly degrading tensile properties consisting essentially of:

a. providing a copper base alloy having a stacking fault energy of less than 30 ergs per square centimeter consisting essentially of a first element selected from the group consisting of about 2 to 12 percent aluminum, about 2 mo percent germanium, about 2 to 10 percent gallium, about 3 to 12 v percent indium, about 1 to 5 percent silicon, about 4 to 12 percent tin, about 8 to 37 percent zinc, and

I I the'balance essentially copper; I

b. cold working said alloy from about 10 to 97. percent; 7 Y

c. forming saidalloy into a desired final article;

d. heating said alloy without significantly degrading tensile properties to a temperature of from about 200 to 360C for at least 1 minute; and

e: cooling said alloy to room temperature, therebyimproving the. creep resistance and the stress relaxation resistance of said article.

2. A process according to claim 1 including the following step subsequent to said cold working step (b) but prior'to said forming step (c): (f) heating said alloy without significantly degrading tensile properties to a a 8 7 cent iron, about 0.01 to 12 percent cobalt, assassins 3.5percent zirconium, about 0.01 to 8.5 percent-manganese.

' 6.A process as in claim 2 wherein said alloy is cold worked from about 15 to 95 percent.

7. A process as in claim 2 wherein said heating steps are at a temperature of from about 220 to 350C.

' grading tensile properties consisting essentially of:

temperature 'of from about 200 to 360C for at least one minute.

3.. A process as in claim 2 wherein said alloy includes at least one second element, different from said first el ement, said second element selected from the group consisting of about 0.001 to 10 percent aluminum,

about 0.,001-v to 4 percent germanium, about 0.001 to 8 percent gallium, about 0.001 to 10 percent indium, about 0.001 to 4 percent silicon, about0.00l to 10 percent tin, about 0.001 to 37 percent zinc, about 0.001 I 4, A process as in claim 2 wherein said first element v is selected from the group consisting of about 2 to 10 percent aluminum, about 3 to 5 percent germanium,

about 3 to 8 percent gallium, about 4 to 10 percent indium,'about L5 to 4 percent silicon, about 4 to 10 percent tin, and about 15 to 37 percent zinc.

'5. Av process as in claim 2 wherein said at least one second element is selected from the group consisting of a. providing a copper base alloy having a stacking fault energy of less than 30 ergs per square centimeter consisting essentially ofafirst element selected from the group consistingof about 2 to 12 percent aluminum, -about 2 to 6 percent germanium, about 2 to 10 percent'gallium, about3 to 12 percent indium, about 1 to 5 percent silicon, about 4 to 12 percent tin, about 8 to 37 percent zinc, and

the balance essentiallycopper; a

cold working saidalloy from about 10 to 97 percent; v

c. annealing said alloy for at least one minute at a temperature'of from about 300 to 750C so as to recrystallize said alloy;

(1. cold rolling said alloy from 10 to 97 percent; I

e. forming said'alloyint'o a desired final article;

f. heating said alloy without significantly degrading tensile properties to a temperature of from about 200 to 360C for at least 1 minute; and

g. cooling said alloy to room temperature, f

thereby improving the creep resistance and the stress relaxation resistance of said article. r 11. A process according to claim 10 including the fol lowing step subsequent to said cold working step (d) about .01 to 4 percent aluminum, about 0.01 to 3 percent germanium. about 0.01 to 7 percent gallium, "about'0.0l to 9 percent indium, about 0.01 to 3.5 percent silicon, about 0.01 to 8 percent tin, about 0.01 to 35 percent zinc, about 0.01 to 20 percent nickel, about but prior to said forming step (e): (h) heating said alloy without significantly degrading tensile properties to a temperature 'of from about 200 to 360C for at least one minute. I

12.'A processes inclaim'll wherein said alloy includes at least one second element, different from said first element, said second element selectedfrom the group consisting of about 0.001 to 10 percent aluminum, about 0.001 to 4 percent germanium, about 0.001 to 8 percent gallium, about 0.001 to 10 percent indium, about 0.001 to 4 percent silicon, about 0.001 to 10 percent tin, about 0.001 to 37 percent zinc,about'0.00l to 25 percentnickel, about 0.001' to 0.4 percent phosphorus,about 0.001 to 5 percent iron, about 0.001 to 5 percentcobalt, about 0.00l to 5 percent zirconium, about 0.001 to 10 percent manganese, and mixtures thereof.

13. A process as in claim 11 wherein said first elenium, about 3 to 8 percent gallium, about 4 to 10 per- 0.01 to 0.35 percent phosphorus, about 0.01 to 3.5per- 10 percent tin, and about l5 to 37 percent zinc.

14. A process as in claim 13 wherein said at least one second element is selected from the group consisting of about 0.01 to 4 percent aluminum, about 0.01 to 3 per- 16. A process as in claim wherein said alloy is heated in steps (f) and (h) to a temperature of from 220 to 350C.

17. A process as in claim 16 wherein said alloy is 35 percent zinc, about 0.01 to 20 percent nickel, about 5 heated in steps (f) and (h) for at least 15 minutes. 0.01 to 0.35 percent phosphorus, about 0.01 to 3.5 peri cent iron, about 0.01 to 2 percent cobalt, about 0.01 to 3.5 percent zirconium, about 0.01 to 8.5 percent manganese.

15. A process as in claim 11 wherein said alloy is cold worked in said cold working steps from about 15 to 95 percent.

18. A process as in claim 11 wherein prior to step (d) the grain size of said alloy is increased to at least 0.006 m l imst 7 19. A process as in claim 11 wherein steps (b) and (c) are repeated at least once.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. I 9 Dated- 5 97 Inventor) Eugen-e Shapiro and Jacob Crane It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the "ABSTRACT", lines 3 and 1, "from about 10 to 90 percent" sho'trld read ---from about 10 to 97 'peroent---;

In the 'lABSTRACT", line A, "from about 25-9150 360C" should readff- -ffrom about 200 to 360C--.

In Columh 6', line 28, "CDA Alloy 668" should read ---CDA Alloy-"63$".

Signed and sealed this 21st day of January 1975.

(SEAL) Attest:

MCCOY M. GIBSON-JR}. c. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PC4050 (10-69) USCOMM-DC 60376-P69 0.5. GOVERNMENT PRINTING OFFICE: 1959 0-366-334

Claims

1. A PROCESS FOR IMPROVING THE CREEP RESISTANCE AND THE STRESS RELAXATION RESISTANCE OF COPPER BASE ALLOYS HAVING LOW STACKING FLAUT ENERGY WITHOUT SIGNIFICANTLY DEGRADING TENSILE PROPERTIES CONSISTING ESSENTIALLY OF: A. PROVIDING A COPPER BASE ALLOY HAVING A STACKING FAULT ENERGY OF LESS THAN 30 ERGS PER SQUARE CENTIMETER CONSISTING ESSENTIALLY OF A FIRST ELEMENT SELECTED FROM THE GROUP CONSISTING OF ABOUT 2 TO 12 PERCENT ALUMINUM, ABOUT 2 TO 6 PERCENT GERMANIUM, ABOUT 2 TO 10 PERCENT GALLIUM, ABOUT 3 TO 12 PERCENT INDIUM, ABOUT 1 TO 5 PERCENT SILICON, ABOUT 4 TO 14 PERCENT TIN, ABOUT 8 TO 37 PERCENT ZINC, AND THE BALANCE ESSENTIALLY COPPER; B. COLD WORKING SAID ALLOY FROM ABOUT 10 TO 97 PERCENT; C. FORMING SAID ALLOY INTO A DESIRED FINAL ARTICLE; D. HEATING SAID ALLOY WITHOUT SIGNIFICANTLY DEGRADING TENSILE PROPERTIES TO A TEMPERATURE OF FROM ABOUT 200* TO 360*C FOR AT LEAST 1 MINUTE; AND E. COOLING SAID ALLOY TO ROOM TEMPERATURE, THEREBY IMPROVING THE CREEP RESISTANCE AND THE STRESS RELAXATION RESISTANCE OF SAID ARTICLE.

2. A process according to claim 1 including the following step subsequent to said cold working step (b) but prior to said forming step (c): (f) heating said alloy without significantly degrading tensile properties to a temperature of from about 200* to 360*C for at least one minute.

3. A process as in claim 2 wherein said alloy includes at least one second element, different from said first element, said second element selected from the group consisting of about 0.001 to 10 percent aluminum, about 0.001 to 4 percent germanium, about 0.001 to 8 percent gallium, about 0.001 to 10 percent indium, about 0.001 to 4 percent silicon, about 0.001 to 10 percent tin, about 0.001 to 37 percent zinc, about 0.001 to 25 percent nickel, about 0.001 to 0.4 percent phosphorus, about 0.001 to 5 percent iron, about 0.001 to 5 percent cobalt, about 0.001 to 5 percent zirconium, about 0.001 to 10 percent manganese, and mixtures thereof.

4. A process as in claim 2 wherein said first element is selected from the group consisting of about 2 to 10 percent aluminum, about 3 to 5 percent germanium, about 3 to 8 percent gallium, about 4 to 10 percent indium, about 1.5 to 4 percent silicon, about 4 to 10 percent tin, and about 15 to 37 percent zinc.

5. A process as in claim 2 wherein said at least one second element is selected from the group consisting of about .01 to 4 percent aluminum, about 0.01 to 3 percent germanium, about 0.01 to 7 percent gallium, about 0.01 to 9 percent indium, about 0.01 to 3.5 percent silicon, about 0.01 to 8 percent tin, about 0.01 to 35 percent zinc, about 0.01 to 20 percent nickel, about 0.01 to 0.35 percent phosphorus, about 0.01 to 3.5 percent iron, about 0.01 to 2 percent cobalt, about 0.01 to 3.5 percent zirconium, about 0.01 to 8.5 percent manganese.

6. A process as in claim 2 wherein said alloy is cold worked from about 15 to 95 percent.

7. A process as in claim 2 wherein said heating steps are at a temperature of from about 220* to 350*C.

8. A process as in claim 7 wherein said heating steps are For at least 15 minutes.

9. A process as in claim 2 wherein prior to step (b) the grain size of said alloy is increased to at least 0.006 millimeters.

10. A process for improving the creep resistance and stress relaxation resistance of copper base alloys having a low stacking fault energy without significantly degrading tensile properties consisting essentially of: a. providing a copper base alloy having a stacking fault energy of less than 30 ergs per square centimeter consisting essentially of a first element selected from the group consisting of about 2 to 12 percent aluminum, about 2 to 6 percent germanium, about 2 to 10 percent gallium, about 3 to 12 percent indium, about 1 to 5 percent silicon, about 4 to 12 percent tin, about 8 to 37 percent zinc, and the balance essentially copper; b. cold working said alloy from about 10 to 97 percent; c. annealing said alloy for at least one minute at a temperature of from about 300* to 750*C so as to recrystallize said alloy; d. cold rolling said alloy from 10 to 97 percent; e. forming said alloy into a desired final article; f. heating said alloy without significantly degrading tensile properties to a temperature of from about 200* to 360*C for at least 1 minute; and g. cooling said alloy to room temperature, thereby improving the creep resistance and the stress relaxation resistance of said article.

11. A process according to claim 10 including the following step subsequent to said cold working step (d) but prior to said forming step (e): (h) heating said alloy without significantly degrading tensile properties to a temperature of from about 200* to 360*C for at least one minute.

12. A process as in claim 11 wherein said alloy includes at least one second element, different from said first element, said second element selected from the group consisting of about 0.001 to 10 percent aluminum, about 0.001 to 4 percent germanium, about 0.001 to 8 percent gallium, about 0.001 to 10 percent indium, about 0.001 to 4 percent silicon, about 0.001 to 10 percent tin, about 0.001 to 37 percent zinc, about 0.001 to 25 percent nickel, about 0.001 to 0.4 percent phosphorus, about 0.001 to 5 percent iron, about 0.001 to 5 percent cobalt, about 0.001 to 5 percent zirconium, about 0.001 to 10 percent manganese, and mixtures thereof.

13. A process as in claim 11 wherein said first element is selected from the group consisting of about 2 to 10 percent aluminum, about 3 to 5 percent germanium, about 3 to 8 percent gallium, about 4 to 10 percent indium, about 1.5 to 4 percent silicon, about 4 to 10 percent tin, and about 15 to 37 percent zinc.

14. A process as in claim 13 wherein said at least one second element is selected from the group consisting of about 0.01 to 4 percent aluminum, about 0.01 to 3 percent germanium, about 0.01 to 7 percent gallium, about 0.01 to 9 percent indium, about 0.01 to 3.5 percent silicon, about 0.01 to 8 percent tin, about 0.01 to 35 percent zinc, about 0.01 to 20 percent nickel, about 0.01 to 0.35 percent phosphorus, about 0.01 to 3.5 percent iron, about 0.01 to 2 percent cobalt, about 0.01 to 3.5 percent zirconium, about 0.01 to 8.5 percent manganese.

16. A process as in claim 15 wherein said alloy is heated in steps (f) and (h) to a temperature of from 220* to 350*C.

17. A process as in claim 16 wherein said alloy is heated in steps (f) and (h) for at least 15 minutes.

18. A process as in claim 11 wherein prior to step (d) the grain size of said alloy is increased to at least 0.006 millimeters.

19. A process as in claim 11 wherein steps (b) and (c) are repeated at least once.