US3632454A - Process for inducing superplasticity in zinc or zinc-aluminum alloys containing copper - Google Patents

Process for inducing superplasticity in zinc or zinc-aluminum alloys containing copper Download PDF

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US3632454A
US3632454A US21309A US3632454DA US3632454A US 3632454 A US3632454 A US 3632454A US 21309 A US21309 A US 21309A US 3632454D A US3632454D A US 3632454DA US 3632454 A US3632454 A US 3632454A
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percent
zinc
ingot
temperature
alloy
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US21309A
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James C Marshall
Terrence J Stewart
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International Business Machines Corp
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International Business Machines Corp
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    • 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
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/165—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon of zinc or cadmium or alloys based thereon

Definitions

  • m is the index of strain rate sensitivity in the expression where o-represents stress in pounds per unitarea, 5 represents strain rate in terms of change per unit gauge length per unit time, and K represents a proportionality constant which is approximately equal to the stress required to deform the material at unit strain rate.
  • K depends upon specific dimensions for the other variables. Values for m can be determined by either of two tests; torsionally as described in an article Determination of Strain-Hardening Characteristics by Torsion Testing by D. S. Fields, Jr. and W. A.
  • m in those metals usually employed for superplastic deformation range from 0.3 to 0.8 in which an increasing value indicates greater surface area increase with more uniform thickness. These values are an index of the total available deformation and thickness uniformity. Values of 0.3 and over indicate that satisfactory complex shapes may be formed.
  • metal alloys found to be hyperextensible, hence well-suited to deformation by super plastic techniques are indicated as 78 to 80 zinc with to 22 percent aluminum and 66 to 68 percent with 32 to 34 percent copper. (Percentages are by weight.)
  • the first alloy is the one most used.
  • the second is brittle at room temperature and has a narrow working temperature.
  • Brass zinc with 52 percent to 62 percent copper
  • zinc-aluminum alloys can contain small amounts of other metals without deteriment to the superplastic characteristics. For instance, manganese or magnesium can be added in amounts up to 0.3 percent, and chromium or nickel can be added up to 0.5 percent. These metals usually improve alloy strength. Copper in small amounts, usually below 1 percent, has been added to these alloys because of its known effect in reducing and improving resistance to creep. Copper additions beyond this limit are readily noticeable by the greater forming energies necessary. Cold rolling reductions are limited to approximately 25 percent when these minor additions are present, compared to the 75-90 percent usually possible with the binary zinc-aluminum.
  • a primary object of out invention isto provide a treatment process for metals containing significant amounts of copper to achieve the characteristics of superplasticity similar to those in the alloys having only minor quantities of copper.
  • Another important object of our invention is to provide a process for treating metals which will enable the fabrication thereof by the usual superplastic deformation techniques and possess markedly superior resistance to creep and corrosion and exhibit greater tensile'streng'th.
  • a further object of our invention is to provide a processing technique for zinc-aluminum alloys with a relatively high copper content which will maintain m and K substantially at those values determined for a zinc-aluminum alloy without copper and thus enable the use of conventional superplastic deformation practices during fabrications.
  • FIG. 1 is a composition diagram of an exemplary alloy range suitable for treatment in accordance with the invention.
  • FIG. 2 is a comparative data plot of stress vs. strain rate to demonstrate the effect of m and K on the energy requirement for superplastic deformation.
  • alloys are considered as superplastic when they can be subjected to unusual elongations without necking and with a substantially uniform thickness after superplastic deformation having a variation within 10 percent.
  • the proportion of aluminum appears to be significant in selecting the working temperature.
  • the maximum temperature is 530 F. due to transformation above that limit.
  • the preferred working range is broadened and raised to between approximately 300 and 500 F; an upper limit in this case is 600 F. due to grain growth. In alloys containing only zinc and copper the acceptable temperature can reach 700 F.
  • Warm reduction is not limited to particulartypes of working.
  • the working can be accomplished by extrusion, rolling or other standard techniques such as swaging or drawing. Extrusion, however, appears to be more effective than rolling or swaging for those alloys having low amounts of aluminum, such as below about 15 percent It has been found that lower values of the strain rate coefficient, K, can be obtained. Alloys having a larger proportion of aluminum do not shown any significant change in K when the method of working is changed.
  • the value of the strain rate coefficient, K is generally higher for the zinc-copper alloys than for the standard zinc-22 percent aluminum.
  • the value of K is approximately equal to the stress required to deform the material at a beneficial in lowering the value of K when the aluminum con- 5 strain rate of l in./in./min.
  • tent again is gr at t an abOut as in the 6888 Of that higher forming forces will probably be required, the zincsion. This effect on alloys with less aluminum 15 only minor.
  • m is the slope of the Process be In the e area Show" i the eompesmeh curve for the alloy, and thus curve 11 is steeper for the zincgtam of e hmlts are approximately from 0 Percent 15 copper.
  • the strain rates below the cross over point for the to 36 Percent ahlmthum and 6 Pe to 12 Pe p curves indicate the stress required to deform the zinc-copper with Zinc composing h l' m Aluminum Content alloy is less than that for the zinc-aluminum alloy.
  • magnesium Comparison of several characteristics of various zincm n e, hromi m a d i kel whi h m y b add d i copper-aluminum alloys treated in accordance with ur warm amounts up to 1 percent. Preferred amounts are 0.01 percent reduction process is given below in the table. As a control for magnesium 0.3 percent for manganese, 0.3 percent for these characteristics are also given for the standard 78 percent chromium and 1 percent for nickel. zinc-22 percent aluminum alloy, which is commonly used for Mmorpaddltlons of magnoslum, manganese or chromium superplastic forming, and for 100 percent zinc.
  • Temperatures specified in the table are those at which superplastic tensile elongation tests were conducted. The elongations attained during the tests are indicated as either greater than 200 or 1,000 percent because the tests were terminated at those values. A specimen successfully concluded the elongation set forth and would have a limit of elongation at some value exceeding that given. Alloys of each general group were subjected to a deformation test by forming in a rectangular die 3 in. x 3 in. X5 in. Formation was accomplished according to the technique of US. Pat. No. 3,340,101 above.
  • the specimens were all prepared from cast ingots of 1.5 in. diameter which were subjected to either warm extrusion of warm rolling, or both, as indicated.
  • the ingot was reduced from 1.5 in. to 0.3 in. diameter by extrusion and then warm rolled to 0.05 in. thickness.
  • the ingot was side forged to 0.4 in. and warm rolled to 0.05 in. thickness Generally extrusion has been found more effective for thorough working.
  • a .zinc-copper alloy with 8-10 percent-copper without these additions exhibit a creep rate from 75 percent to percent per 10,000 hours at a loading of 10,000 p.s.i. With the additives present the creep rate is radically reduced to less than 0.1 percent under the same conditions. These rates are significantly better than the creep rate of 10 percent for the standard heat-treated zincaluminum alloy. Impurity additions like the foregoing have the same effect when added to alloys containing aluminum, copper in the same proportion, and less zinc. Without these additions, he creep rate of zinc-copper-aluminum alloys approximates that of the standard zinc-aluminum.
  • Tensile strength also improves with the additions of copper. While the standard zinc-aluminum eutectoid alloy has a tensile strength of approximately 43,000 p.s.i., that of alloys containing 8-12 percent copper was from 53,000 to 56,000 p.s.i. The presence of the above minor additives further increased this strength to a range of 56,000 to 78,000 p.s.i.
  • Alloys of zinc-copper have been found to not require heat treatment after thermoforming. This. advantageously eliminates a processing step-in fabrication. When the alloy contains aluminum, however, the benefit of heat treatment increases in proportion to the aluminum content.
  • the invention offers an important advantage with regard to secondary processing steps.
  • the alloys having less than approximately 5 percent aluminum can be subjected to such secondary steps as plating, painting, welding and soldering using standard zinc die cast procedures. Additionally the forming temperatures are kept low because alloys are zincbased.
  • a process of producing stock suitable for superplastic deformation from a zinc alloy nominally containing, by weight, from 6 to 12 percent copper and 0 percent to 36 percent aluminum comprising the steps of:
  • a process of making metal forms comprising the steps of:
  • a process of making metal forms comprising the steps of:

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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)
  • Organic Chemistry (AREA)
  • Forging (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
  • Heat Treatment Of Nonferrous Metals Or Alloys (AREA)
US21309A 1970-03-20 1970-03-20 Process for inducing superplasticity in zinc or zinc-aluminum alloys containing copper Expired - Lifetime US3632454A (en)

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US (1) US3632454A (enrdf_load_stackoverflow)
JP (1) JPS5248092B1 (enrdf_load_stackoverflow)
CA (1) CA948080A (enrdf_load_stackoverflow)
DE (1) DE2112370C2 (enrdf_load_stackoverflow)
FR (1) FR2083894A5 (enrdf_load_stackoverflow)
GB (1) GB1303957A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3793091A (en) * 1971-08-20 1974-02-19 Noranda Mines Ltd Superplastic conditioning of ternary and quaternary zinc-aluminum alloys

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8521017D0 (en) * 1985-08-22 1985-10-16 Bnf Metals technology centre alloy

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3340101A (en) * 1965-04-02 1967-09-05 Ibm Thermoforming of metals
US3420717A (en) * 1966-03-28 1969-01-07 Ibm Metal softening process and product thereof

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3340101A (en) * 1965-04-02 1967-09-05 Ibm Thermoforming of metals
US3420717A (en) * 1966-03-28 1969-01-07 Ibm Metal softening process and product thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3793091A (en) * 1971-08-20 1974-02-19 Noranda Mines Ltd Superplastic conditioning of ternary and quaternary zinc-aluminum alloys

Also Published As

Publication number Publication date
GB1303957A (enrdf_load_stackoverflow) 1973-01-24
FR2083894A5 (enrdf_load_stackoverflow) 1971-12-17
DE2112370A1 (de) 1971-10-07
JPS5248092B1 (enrdf_load_stackoverflow) 1977-12-07
DE2112370C2 (de) 1985-01-17
CA948080A (en) 1974-05-28

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