SPRINGS WITH 2-WAY SHAPE-MEMORY OBTAINED BY STABILIZED STRESS-INDUCEDMARTENSITE TRAINING METHODS

The influence of the amount of deformation induced during training and the time elapsed between quenching after betatising and training of t he two way shape memory effect (TWSME) developed in Cu-Zn-Al shape mem ory compression springs is studied. Training was carried out by the co nstraint ageing (stabilised stress induced martensite) method and TWSM E was assessed by thermal cycling between 20 degrees C and 100 degrees C. An increase in TWSME is obtained on increasing training strain. Th is is a consequence of the greater volume of material trained at highe r training strains. The time between quenching and the commencement of training affects substantially the amount of TWSME developed. This is a consequence of the quenched in vacancy supersaturation enhacing the ''stabilisation''(1) of the thermal martensite originally formed on q uenching.