Phase analysis of NiTi shape memory wires and computer simulations of the superelastic effect

Abstract

Shape memory alloys belong to the group of intelligent materials due to their exceptional properties related to reversible martensitic transformation. They show both superelasticity and shape memory effects. The modelling of the superelastic phenomena occurring in NiTi alloys is important due to its application in the further development of materials for dedicated applications. A computer simulation of static tensile test was carried out using the finite element method for NiTi wire and obtained results were compared with experimental curve. For the determination of phase composition at ambient temperature and courses of phase transitions during cooling and heating the X-ray powder diffraction and differential scanning calorimetry methods were used. X-ray diffraction phase analysis exhibited that the studied wire at room temperature has B2 — parent phase structure. Additionally, differential scanning calorimetry measurements showed that the phase transformations during cooling and heating occur in a temperature range of about –20 to +30 C.