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Method of processing nickel-titanium-base shape-memory alloys and structure

  • US 4,533,411 A
  • Filed: 11/15/1983
  • Issued: 08/06/1985
  • Est. Priority Date: 11/15/1983
  • Status: Expired due to Term
First Claim
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1. A method of processing nickel-titanium-base shape-memory alloys to substantially suppress the two-way effect which comprises:

  • providing a nickel-titanium-based shape-memory alloy in the austenitic state in a specified shape;

    cold working said alloy in the martensitic state from 15% to 40% to provide a microstructure containing a high concentration of substantially random dislocations;

    annealing said alloy without restraint at 300°

    C. to 500°

    C. for at least 20 minutes to rearrange the dislocations into an ordered network of dislocations comprising essentially dislocation-free cells surrounded by walls of higher dislocation density;

    providing said alloy in a desired shape while maintaining the dislocation-free cells obtained in the annealing step; and

    deforming the alloy in the martensitic state;

    whereby when the alloy is recovered by heating the alloy to the austenitic state and subsequently cooled to the martensitic state, the alloy substantially retains said desired shape.

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