Shape memory characteristics of TiNi casting alloys made by using self-propagating high-temperature synthesis

Self-propagating high-temperature synthesis (SHS) is a new method of making an ingot of TiNi. This method shows little gravity segregation. The purpose of this study is to investigate the difference of the shape memory characteristics of the TiNi casting alloys made from a SHS ingot and from a conventional melt cast ingot. The samples used in this study were rods made by centrifugal casting. Differential scanning calorimetry (DSC), X-ray diffraction, and tensile test were used to examine the shape memory characteristics on the samples. The heat treatment conditions were 773 K-1.8 ks and 1073 K-3.6 ks, respectively. The DSC samples were both ends (the top and bottom area) of the rod samples. The results of the XRD measurements showed that TiNi phase was obtained in all the samples. In contrast, the result of the DSC test showed that more gravity segregation effect happened in the melt cast sample than in the SHS sample. As the conclusion of this study, gravity segregation had little effect in the SHS ingot sample