Process for the production of two-way shape memory alloys

Abstract

The present invention for producing a substantial two-way shape memory effect within a composition substantially only exhibiting one-way memory is realized by first plastically deforming the alloy into a predetermined shape and then work hardening, such as through grit blasting, a selected portion of the outer surface of the alloy. Advantageously, this later type of work hardening selectively transforms only the outer portion of the alloy into a region of "super-elasticity" which acts as a biasing force to re-strain the alloy upon cooling. As such, two-way shape memory elements--which recover their original shape upon heating, yet deform into a second desired shape upon cooling--may be made to produce actuators exhibiting strain amplitudes of as much as 3% while exerting a force in excess of about 10,000 psi. Moreover, the alloy elements may be judiciously processed to perform movement in direct tension, expansion, bending, or torsion or any combination thereof while exerting force, and operating over large cycle numbers.

Dependencies are inferred from the claim text.