Effect of thermal cycling on the shape memory transformation behavior of NiTi alloy: Powder X-ray diffraction study

The results of studies carried out on the effect of thermal cycling on the phase transformation behavior of Ni-rich NiTi shape memory alloy (SMA), using powder X-ray diffraction (XRD) technique, are presented in this article. In Ni-rich NiTi alloy heat-treated at 660 °C, the integrated peak area (integrated intensity) corresponding to (1 1 0)A plane of the austenitic phase increases and the area corresponding to martensitic phase decreases with increasing temperature. Austenitic start and finish temperatures change during the first few thermal cycles. The former decreases by ∼15 °C and the latter decreases by ∼35 °C during the first cycle, whereas martensitic start and finish temperatures do not get affected by thermal cycling. The transformation characteristics determined through XRD are compared with those obtained from differential scanning calorimetry (DSC).