The transformation behavior and the shape memory effect due to cyclic stress/strain for Ti–49.6Ni alloy

Abstract

The transformation behavior for Ti–49.6 at.%Ni shape memory alloy was investigated under cyclic stress/strain by electrical resistance method and differential scanning calorimetry (DSC) method. After solution no R transformation occurred during the martensite transformation in the R– T curve, and the reverse martensite transformation temperature points A s as well as A f could be discerned clearly in the heating process. With the same kind of heat treatment, R transformation occurred after the specimen underwent cyclic stress or strain; in the meantime, the reverse transformation temperature points A s and A f were illegible during the reverse martensite transformation. The characteristics of resistance–temperature curve ( R– T curve) of Ti–49.6Ni shape memory alloy changed apparently and regularly. The results also showed that after cyclic strain, the transformation temperatures M s and A s were stable while the cyclic stress is not. That implied that the low-strain cycling itself could be used as a better method for mechanical training. For both stress and train cycling, the martensite transformation temperature M s was lower than that of the raw material. It indicated that stress/strain cycling would inhibit the martensite transformation and directly result in the R transformation occurring. The shape memory effect after cyclic stress/strain were also studied, respectively.