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
  • C22F1/16—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
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S420/00—Alloys or metallic compositions
  • Y10S420/902—Superplastic

Definitions

• vvherein '11 represents stress in load per unit area
• K represents a constant which is termed the strain rate coefficient.
• the strain rate coefficient K is significant in determining the strength of the material and hence the amount of work required to form the part.
• Processes for rendering a zinc/aluminium alloy superplastic comprise heat treating the alloy at a temperature above 275 C for a period of time to allow the alloy to become substantially homogenous, quenching or similarly rapidly cooling the alloy and mechanically working the cooled alloy at a temperature below 275 C.
• the present invention consists in a process for providing superplastic properties in alloys of zinc and aluminium, comprising a. heat-treating a body of the alloy containing between 18' and 40 percent by weight of aluminium, the remainder being zinc together with any incidental impurities and minor ternary alloying components and the alloy composition and temperature being such as to fall within the aluminium rich single-phase region of the zinc-aluminium phase diagram, until a substantially ho mogeneous structure is obtained, and thereafter characterized by:
• the reduction is more preferably at least 92 percent, or at least 94 percent; that is to say, the dimensions of the work piece are less than 10 percent, and preferably less than 6 percent, those of the original body of alloy.
• Working is preferably effected by rolling.
• the cooling rate of less than 10 C per minute is greatly different from a quenching rate, which is usually several degrees per second. It can be achieved by cooling in air (normally in still air) or by cooling by discontinuing the supply of heat to the heat-treating zone, such as a furnace, and allowing the whole environment of this nature to cool. Furnace cooling is generally slower than air cooling; preferably a cooling rate of 3 to 5 C per minute is utilized.
• a key feature of this invention is the combination of the manipulative steps of cooling and working, carried out with reference to the temperature range of 200 to 275 C and preferably 200 to 250 C.
• some of the working may be effected above 275 C but most in the range 200 275 C, or all of the working can be effected in this range.
• the body of alloy is reheated to above 200 C and subsequently at least part of said total reduction is carried out at below 275 C, other possibilities present themselves.
• all of the (at least 90 percent) reduction can be effected after such reheating.
• Another aspect of the invention is the superplastic alloy produced by the above process. To be generally useful, this should have a vacuum forming time, measured for a sheet 0.05 inches thick by the method described below, of below 350 seconds; however, this value is not critical, and depends upon the intended end use of the material. Thickness of sample affects this VFT, although not in a linear fashion.
• Such an alloy can be of zinc and aluminium with only incidental impurities.
• the eutectoid composition can be used, but the so-called /30 zinc/aluminium alloy, within the compositional tolerances common in this art, has also been found valuable.
• Ternary alloying components can be used; thus magnesium can be present,:e.g., in amounts up to 0.1 percent by weight (specifically 0.01 percent) in amounts up to 1.0 percent by weight, specif cally0.5 percent.
• VFI' Vacuum forming time
• EXAMPLE 1 A body of alloy 0.75 inches thick containing by weight 70 percent zinc, 30 percent aluminium and 0.5 percent copper (measured on the basis of zinc and aluminium present) was annealed at 375 C for 5 hours, air-cooled to room temperature, reheated to 250 C and rolled to 0.05 inches thick at this temperature. The vacuum forming time was 255 seconds.
• EXAMPLE 9 This illustrates that the initial type of alloy body has some effect on results, but that the invention is of general applicability.
• Rolling slabs of 0.75 inches thickness produced by (A) gravity casting and (B) direct chill semicontinuous casting, and of 70/30 zinc/aluminium composition were annealed at 375 C and then air-cooled to room temperature. They were then reheated to, and rolled at, 250 C to 0.05 inches. Results were as follows:
• Annealing Time in Hours VF! in Seconds (A) (B) 1 H 270 465 16 245 2
• Gravity-cast slabs of /30 zinc/aluminium alloy were annealed then 5 hours at 375 C. Thereafter they were subjected to different procedures.
• One slab was air-cooled and aged for 24 hours at room temperature and then reheated to and rolled at 250 C to 0.05 inches. It had a VFT of 285 seconds.
• the other slab was not cooled, but rolled at 375 C to 0.375 inches and then air-cooled and aged for 24 hours at room temperature before being reheated to, and rolled at 250 C to 0.05 inches. It had a VFT of 720 seconds.
• a process for providing superplastic properties in alloys of zinc and aluminium comprising:

Landscapes

• 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)
• Metal Rolling (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Heat Treatment Of Nonferrous Metals Or Alloys (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9697111

Family Applications (1)

Country Status (5)

Cited By (4)

Families Citing this family (1)

Citations (6)

• 1970
  • 1970-01-01 GB GB2970A patent/GB1297101A/en not_active Expired
  • 1970-12-29 JP JP45125180A patent/JPS5011847B1/ja active Pending
  • 1970-12-31 DE DE2064741A patent/DE2064741C3/de not_active Expired
  • 1970-12-31 FR FR7047448A patent/FR2075148A5/fr not_active Expired
• 1971
  • 1971-01-04 US US00103911A patent/US3753791A/en not_active Expired - Lifetime

Patent Citations (6)

Also Published As

Similar Documents