Optimization of thermal treatment parameters to alter austenitic phase transition temperature of NiTi alloy for medical implant

Super-elasticity (SE) of nickel titanium alloy is usually achieved by thermal or thermo-mechanical treatment. This SE property depends on reverse martensitic transformation; however, previous studies rarely focused on the effect of heat treatment on the transformation characteristics to the austenite phase. In this study, we aim to explore this relationship because there are numerous developed and potential medical applications utilizing the SE properties of shape memory alloy (SMA) recently. Over 70 specimens heat treated using different treatment parameters were carefully prepared and analyzed by differential scanning calorimeter (DSC). We found that the austenite phase transition temperature (As, Ap and Af) can be manipulated by varying the heat treatment parameters such as heat treatment time, temperature and cooling rate. This is important for the production of NiTi SMA implants with desired SE properties at body temperature.