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

The effect of thermal cycling under loading on martensitic transformation a nd two-way shape memory effect was investigated for Ti-49.8 at, pet Ni allo y. It is shown that M-s, and M-f temperature increase with increasing the n umber of cycles, while A(s) and A(f) temperature decrease during thermal cy cling. The total strain at and permanent strain epsilon (p) increase with i ncreasing applied stress and number of cycles. The two-way shape memory eff ect can be improved by proper thermal cycling training under loading, while excessively high applied stress results in the deterioration of TWSME. The reason for the changes in martensitic transformation characteristics and t wo-way shape memory effect during thermal cycling under loading is discusse d based on the analysis of microstructure by TEM observations.