Relationship between the variation in transformation temperatures, resistivity and dislocation density during thermal cycling of Ni50Ti50 shape memory alloy

The aim of the present work is to find the relationship between a decrease in transformation temperature and an increase in dislocation density during thermal cycling of NiTi alloy. The resistivity is used as a measure of the dislocation density variation and it allows one to find a linear dependence of the increment in the transformation temperatures on the dislocation density variation starting with the fifth thermal cycle. It is found that the thermal cycling of NiTi alloy within a temperature range of 473 to 273 K is accompanied by less dislocation density variation than in a range of 413 to 273 K. The dependence of transformation temperatures on increase in dislocation density in the first five cycles is not linear, hence it is concluded that the dislocation density variation is not the unique reason for a decrease in transformation temperature during the thermal cycling of equiatomic NiTi alloy.