Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon

Definitions

• ABSTRACT OF THE DISCLOSURE A process for improving the elongation of copper base alloys by controlled grain coarsening. Copper base alloys containing from about 2 to about 9.5% aluminum, less than 1% zinc, and a grain refining element such as iron, chromium, zirconium, or cobalt are subjected to a final cold reduction of from about 8% to about 22% and a final anneal of from about 550 to about 715 C. Alternatively, the alloy can be subjected to a sequence of decreasing reductions interspersed with high temperature anneals, followed by the above final reduction and anneal.
• a grain refining element such as iron, chromium, zirconium, or cobalt
• grain refiners it is common practice to add grain refiners to various solid solution, single-phase alloys for the purpose of maintaining a fine grain material during processing from the original cast material to the final wrought condition.
• the grain refiner may be added to improved processing and/ or to improve properties.
• the grain refiner serves to maintain uniform properties over a compositional range and over a range of processing conditions.
• the grain refiners are not completely stable over the full range of temperatures :up to the melting point of the alloys because of decomposition or varying solubility.
• Copper base alloys containing grain refiners maintain a fine grain size over a range of commercially suitable annealing temperatures and over a range of commercially acceptable solute concentrations. These alloys maintain a relatively small variation in mechanical properties over these temperature and composition ranges. This, of course, is a very desirable feature commercially. It does, however, cause certain restrictions in the normally available ductility of the alloy. In contrast thereto, as a solid solution, single-phase alloy without grain refiners is heat treated to higher annealing temperatures, the grain size and the ductility of the alloy increase and the strength decreases.
• annealing temperature is further limited for fabricating parts which require a highly polished surface in that above a certain grain size, an orange peel condition occurs during fabrication which detracts from the appearance of the polished surface.
• a process has been developed which permits certain grain refined copper base alloys to achieve uniform ductility with a controlled grain size.
• the process comprises a final cold reduction of annealed metal of from about 8 to 22 percent, followed by a high temperature anneal or a sequence of decreasing cold reductions interspersed with relatively high temperature anneals.
• the process in accordance with this invention is particularly applicable to copper base alloys containing from about 2 to about 9.5 percent aluminum, less than about 1 percent zinc, and a grain refining element selected from the group consisting of iron .001% to 5.0%, chromium .001% to 1%, zirconium 001% to 1.0%, co balt 001% to 5.0%, and mixtures of these grain refining elements.
• the aforenoted alloys also contain from about .001 to about 3 silicon.
• the alloys processed in accordance with this invention provide markedly improved elongation with a suitably small grain size.
• a process has been developed which permits certain grain refined copper base alloys to achieve improved ductility with a uniformly coarsened grain size.
• the process is particularly applicable to copper base alloys containing from about 2 to about 9.5% aluminum, less than 1% zinc, and a grain refining element selected from the group containing iron .001 to 5.0%, chromium .001 to 1%, zirconium .001 to 1.0%, cobalt .001 to 5.0%, and mixtures of these elements and the balance copper.
• the alloy also contains from about .001 to about 3% silicon, and the aluminum range is from about 2 to about 5%. It has been found that the processing of this invention is particularly applicable to CDA Alloy 638 containing 2.5% to 3.1% aluminum, 1.5% to 2.1% silicon, 0.25% to 0.55% cobalt, and the balance copper.
• an alloy within the aforenoted ranges of composition is provided in the annealed condition, the alloy having been annealed at a temperature of less than 600 C.
• the annealed alloy is subjected to a final cold reduction of from about 8% to about 22%, and preferably from about 10% to about 20%.
• the cold worked alloy is then subjected to a final anneal at a temperature of from about 550 C. to about 715 C., and preferably from about 650 C. to about 700 C.
• aforenoted process yields a wrought alloy having a substantially uniform grain size of less than 0.025 millimeters, an ultimate tensile strength of at least 70 k.s.i., a 0.2% yield strength of at least 30 k.s.i., and an elongation of at least 40%. It has been possible to achieve with CDA Alloy 638 elongations as high as about 45% with an ultimate tensile strength of about 74 k.s.i., and a 0.2% yield strength of about 40 k.s.i.
• the process is carried out in a sequence of cold reductions interspersed with relatively high temperature anneals.
• an alloy within the aforenoted ranges of composition is subjected to an amount of cold work suflicient for it to recrystallize at less than about 600 C.
• this comprises cold reducing the alloy at least and preferably at least 30%.
• the maximum amount of cold work performed is governed by the gage requirements for the alloy.
• the cold worked alloy is then subjected to an intermediate anneal at a temperature of from about 400 to about 600 C., and preferably from about 450 to about 575 C.
• the intermediate annealed alloy is then subjected to a final cold reduction of from about 8% to about 22%, and preferably from about 10% to about 20%.
• the finally cold worked alloy is then subjected to a final anneal at a temperature of from about 550 to about 715 C., and preferably from about 650 to about 700 C.
• an alloy within the aforenoted ranges of composition is subjected to a cold reduction of at least 10%, and preferably at least 30%, depending on gage requirements; the cold worked alloy is then intermediate annealed at a temperature of from about 400 to about 600 C., and preferably at a temperature of from about 450 to about 575 C.
• the annealed alloy is then subjected to a cold reduction of from about 25 to about 40% and then to an intermediate anneal at a temperature of from about 400 to about 600 C., and preferably at a temperature of about 450 to about 575 C.
• the intermediate annealed alloy is then subjected to a final cold reduction of from about 8% to about 22%, and preferably from about 10% to about 20%.
• the finally cold worked alloy is then subjected to a final anneal at a temperature of from about 550 to about 715 C., and preferably at a temperature from about 650 to about 700 C.
• This embodiment of the invention provides greater flexibility in meeting gage requirements in accordance with this invention, and should give more uniform recrystallization of the alloy and more uniform properties.
• the intermediate an- .nealing temperatures are critical if the alloy has previously been subjected to a cold reduction of at least 22%.
• the final cold working and final annealing steps are critical to obtain a wrought alloy having improvide elongation without irregular grain growth.
• the processes of this invention provide uniform grain coarsening and substantially uniform grain sizes of less than .025 millimeters. If the upper limit for the final annealing temperature is exceeded in accordance with this invention, the alloy is subject to irregular grain growth. This is similarly the case with respect to the final cold Working step, since a reduction of greater than 22% will produce the onset of irregular grain growth.
• the times at temperature and the heat up and cool down rates for the annealing steps of this invention are not critical and may be set as desired in accordance with conventional practice for these types of alloys.
• alloys of low stacking fault energy containing dispersed second phase particles e.g. Alloy 638
• a 50% cold reduction results in a strong ⁇ ll0 ⁇ ll2 deformation texture or preferred orientation.
• Alloy 638 is recrystallized at 500 to 600 C., it contains newly formed recrystallized strain-free grains of very small size.
• the strong pinning effect of the CoSi dispersed second phase insures retention of fine grains.
• the pinning force diminishes as the CoSi agglomerates and/ or resolutionizes.
• the ⁇ ll0 ⁇ ll2 type texture has been found to be the stable end texture in cold rolled, low stacking fault energy alloys, such as Alloy 638. Irregular grain growth results in a ⁇ ll0 ⁇ ll2 type annealed texture. It is believed that the development of the irregular grain growth and the 112 annealed texture is related to the presence of a critical amount of ⁇ ll0 ⁇ ll2 deformation texture before the final recrystallization anneal.
• texture or preferred orientation refer to the planes of the grains which are parallel to the strip surface.
• the annealing temperature refers to the temperature of the metal rather than the furnace temperature.
• Example I Samples of CDA Alloy 638 having a composition of 1.98% silicon, 2.5% aluminum, 0.42% cobalt, and the balance copper were prepared by commercial means to 0.090 inch gage. The samples were then processed in accordance with the process sequences in the table following. The mechanical properties and grain sizes for the samples are shown in the table.
• This example shows that a range of elogation and strength properties and uniform grain coarsening which results in a suitably small grain size can be obtained by the processes of this invention.
• Process Sequence A corresponds to conventional processing for this alloy and is not in accordance with the process of this invention. It is presented by way of comparison.
• Processing Sequences B and C illustrate that if the final cold working step is kept within the range of reduction in accordance with this invention, uniform grain coarsening and marked improvements in elongation can be obtained upon final annealing over a range of annealing temperatures.
• Example II Samples of CDA Alloy 638 having a composition of 1.98% silicon, 2.5% aluminum, 0.42% cobalt, and the balance copper were prepared by commercial means to 0.080 gage- The samples were given varying final cold reductions and were annealed at varying final annealing temperatures. The resulting relationships are tabulated below.
• Samples of CDA Alloy 638 having a composition of 1.98% silicon, 2.5 aluminum, 0.42% cobalt, and the balance copper were prepared by commercial means to 0.090 inch gage.
• the samples were processed in accordance with the following sequence, wherein the intermediate annealing temperature was varied. The results are tabulated below.
• This example clearl illustrates the critical nature of the intermediate annealing temperature.
• the example shows that if the intermediate annealing temperature after a cold reduction of at least about 22% exceeds about 600 C., one can expect the onset of exaggerated grain growth.
• a process for improving the elongation of copper base alloys by controlled grain coarsening comprising:
• a copper base alloy containing from about 2 to about 9.5% aluminum, less than about 1% zinc, a grain refining element selected from the group consisting of iron from about .001% to about 5.0%, chromium from about .001% to about 1%, zirconium from about 001% to about 1.0%, cobalt from about .001% to about 5.0%, and mixtures of these elements, and the balance copper, said alloy being in the annealed condition;
• said alloy further contains from about .001 to about 3% silicon, and wherein the aluminum content is from about 2 to about 3.
• a process according to claim 4 wherein the final annealing temperature is from about 650 C. to about 700 C.
• a process for improving the elongation of copper base alloys by controlled grain coarsening comprising:
• said alloy further contains from about .001 to about 3% silicon, and wherein the aluminum content is from about 2 to about 5%.
• said alloy contains 2.5% to 3.1% aluminum, 1.5% to 2.1% silicon, 0.25 to 0.55 cobalt, and the balance copper.
• Step B comprises at least 30% and the intermediate annealing temperature in Step C is from about 450 to about 575 C.
• Step D is from about 10% to about 20% and wherein the final annealing temperature of Step E is from about 650 to about 700 C.
• a process for improving the elongation of copper base alloys by controlled grain coarsening comprising: (A) providing a copper base alloy containing from about 2 to about 9.5% aluminum, less than about 1% zinc, a grain refining element selected from the group consisting of iron from about .001% to about 5.0%, chromium from about .001% to about 1%, zirconium from about .001% to about 1.0%, cobalt from about 001% to about 5.0%, and mixtures of these elements, and the balance copper, said alloy being in the annealed condition;
• Step B is at least 30% and wherein the annealing temperatures in Step C and Step E are from about 450' to about 575 C.
• Step E is from about 10% to about 20% and wherein the annealing temperature in Step F is from about 650 to about 700 C.

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• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
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• Heat Treatment Of Nonferrous Metals Or Alloys (AREA)

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• 1972
  • 1972-11-24 US US00309345A patent/US3788902A/en not_active Expired - Lifetime
• 1973
  • 1973-11-15 GB GB5312773A patent/GB1420795A/en not_active Expired
  • 1973-11-19 AU AU62643/73A patent/AU473298B2/en not_active Expired
  • 1973-11-21 IT IT53811/73A patent/IT997666B/it active
  • 1973-11-22 JP JP13159473A patent/JPS5314490B2/ja not_active Expired
  • 1973-11-22 CA CA186,503A patent/CA1001057A/en not_active Expired
  • 1973-11-22 FR FR7341647A patent/FR2208000B1/fr not_active Expired
  • 1973-11-23 SE SE7315925A patent/SE403628B/xx unknown
  • 1973-11-23 DE DE19732358510 patent/DE2358510B2/de not_active Ceased
  • 1973-11-23 BE BE138120A patent/BE807748A/xx not_active IP Right Cessation
  • 1973-11-23 CH CH1654473A patent/CH582244A5/xx not_active IP Right Cessation

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