Investigating the heat resistant properties of the TiNi shape memory alloy on the B19′→B2 phase transformation using the alloy powder

The high temperature resistance behaviour of the TiNi shape memory alloy (SMA) B19′→B2 phase transformation zone was investigated in TiNi alloy powder. The powder samples were subjected to cyclic thermal treatment in air. Firstly, the TiNi alloy powders were annealed at 500 °C, 600 °C, 700 °C and 800 °C for 6 h in air. On another study, the TiNi alloy powder was annealed at 400 °C for 30 h, 60 h, 90 h and 120 h, respectively. The results shows that annealing the powder above 500 °C suppresses the B19’→B2 phase transformation. On the other hand, the B19’→B2 phase transformation was visible on the 30 h, 60 h, 90 h and 120 h samples annealed at 400 °C. Surface morphologies analyses of the TiNi alloy powders were investigated using a high-resolution scanning electron microscope (HR-SEM, Auriga ZEISS), while the thermal analysis was carried out using DSC in NETZSCH STA.