The heating-cooling rate effect on thermal properties of high nickel-rich NiTi shape memory alloy

In this study, the effects of heating and cooling rate on the thermal properties of high nickel-rich Ni55Ti45 shape memory alloy were investigated. Transformation temperatures and enthalpies were determined by differential scanning calorimetry. R-phase was observed with two-stage phase transformation during cooling. Transformation finish temperatures were affected, while the transformation start temperatures were not changed by heating-cooling rate. Kissinger, Takhor, and Ozawa methods were applied to find activation energy that is needed for phase transformation. The average activation energy value of 200.5 kJ mol(-1) was calculated for Ni55Ti45 alloy. The calculated activation energy was found lower than the ones reported in the literature.