The Effect of Stress Ageing on the Properties of Shape Memory Alloys

The performance characteristics of shape memory alloys operating in an overtemperature shut-off valve at a temperature of 95OC for up to 2000 hours are presented. Alloys of NiTi, Cu-Al-Ni and Cu-Zn-Al have been characterised under these ageing conditions. The effect of altering the processing parameters, viz solution treatment temperature, quenching technique and training procedure were examined. All alloys show degradation of the memory behaviour but results are presented which demonstrate that improvements in degradation can arise by altthe solution treatment temperature and training procedure.