Transformation behavior of a Ti–47Ni–3Cu alloy heat treated under temperature gradient

Abstract

Transformation behavior and shape memory characteristics of temperature gradient anneal (TGA) treated and thermo-mechanically treated (TMT) Ti–47Ni–3Cu(at.%) alloys were investigated by means of differential scanning calorimetry and thermal cycling tests under constant load. Both TGA treated and TMT Ti–47Ni–3Cu alloys showed B2–B19′ transformation behavior. The change in Ms * by 23 K was developed in the TGA treated Ti–47Ni–3Cu alloy along the length of the sample (150 mm). TGA treated Ti–47Ni–3Cu alloy showed perfect shape memory effects. The temperature dependence of elongation (dε/dT) of a TGA treated specimen was in the range of 0.02–0.09% K−1 depending on the amount of applied stress, which was small compared to that of a TMT specimen (0.01–0.18% K−1). The temperature dependence of elongation (dε/dT) of the TGA treated specimen on cooling is almost the same as that on heating, while dε/dT of the TMT specimen on cooling is much smaller than that on heating (0.68% K−1).