Effect of thermal cycling under load on martensite transformation and two-way shape memory effect in a TiNi alloy

The influence of thermal cycling under loading on martensitic transformation and two-way shape memory effect was investigated for Ti-49.8 at pct Ni alloy. It is shown that M_s temperature and M_f temperature increase when increasing the number of cycles, while A_s temperature and A_f temperature decrease during thermal cycling. The total strain ε_t and the permanent strain ε_p increases with the increase of the applied stress and cycle number. The two-way shape memory effect can be improved by proper thermal cycling training under loading, while an excessively high applied stress results in the deterioration of TWSME. The reason for the changes in martensitic transformation characteristics and two-way shape memory effect during thermal cycling under loading is discussed based on the analysis of microstructure by TEM observations.