TRAINING AND THE TWO WAY MEMORY EFFECT IN COPPER BASED SHAPE MEMORY ALLOYS

Abstract

Experimental results giving information about the mechanisms of the two way memory effect are presented. It is shown that local martensite stabilization and true plastic deformations have to be considered as undesirable side-effects of training. The experimental results also indicate that the macroscopic two way memory behaviour is, on a microstructural level, associated with a reproducible and stable martensite formation path. The higher the amount of transformation cycles the better becomes the stability and reproducibility. In accordance with the stable path is that the two way memory effect can withstand considerable forces during the forward transformation (the two way memory can do work during cooling). Another consequence is that the maximum attainable two way memory diminishes when the training procedure is preceded by thermal transformation cycles.