Influence of Heat Treatment Temperature on Phase Transformation Behavior and Mechanical Performance of Ti50Ni39Zr10Nb1 SMA

TheTi50Ni39Zr10Nb1 (at.%) shape memory alloy was heat treated at 873 K, 1073 K, and 1273 K, followed by ice-water quenching. The effects of heat treatment on phase transformation behavior, crystal structure, and mechanical properties were investigated. The differential scanning calorimetry (DSC) analysis determined the transformation enthalpy, entropy, elastic strain energy, and Gibbs free energy changes. The X-ray diffraction (XRD) results indicated grain refinement and improved crystallinity after heat treatment. Vickers hardnessvaluesincreasedcomparedtotheas-castcondition.Theresultsrevealthatbothausteniteandmartensite transformation temperatures increase after heat treatment, with the most pronounced rise observed at 1273 K. It was demonstrated that the heat treatment temperature leads to an increase in hysteresis. Moreover, it is noticeable that both the Gibbs free energy and elastic energy significantly increase after the heat treatment process. In addition, it was observed that increasing the heat treatment temperature significantly increased the microhardness. These results show that heat treatment significantly modifies the transformation characteristics and microstructure of the alloy, leading to improved mechanical and functional properties.