The Two Way Shape Memory Effect in Stabilized and Pseudoelastically Trained Cu-Zn-Al Single Crystals

Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, 8400 S. C. de Bariloche, Argentina

Abstract

The two way shape memory effect (TWME) is generally obtained by a training during which the sample is either temperature or stress cycled through the martensitic transformation, resulting in the introduction of dislocations. The TWME can also be obtained by stress inducing a single variant above the Ms temperature, then stabilizing it and retransforming it on unloading to the high temperature β phase. Even when no retained martensite can be detected by optical microscopy, a perfect TWME is present. It has been speculated that the retained nuclei do only help in the nucleation of the selected variants without being able to do any significant amount of work. Present experiments show that by the latter far simpler method samples can be trained which are capable of doing work. Also the length changes, the Ms, and the work done as a function of the opposing stress for both training methods and different amounts of stabilized martensite have been measured and are reported in this paper.