Phase field simulation on the cyclic degeneration of one-way shape memory effect of NiTi shape memory alloy single crystal

In the framework of thermodynamics and based on the Ginzburg-Landau's theory and crystal plasticity, a three-dimensional phase field model was constructed to predict the cyclic degeneration of the one-way shape memory effect (OWSME) of NiTi shape memory alloy (SMA) single crystal. Two inelastic deformation mechanisms, i.e., austenite plasticity and martensite plasticity were newly introduced into the proposed model in order to describe the martensite transformation- and reorientation-induced plasticity and the stress-strain response of NiTi SMA single crystal more reasonably. From the phase field simulations, it is found that: during the thermo-mechanical cyclic deformation of NiTi SMA single crystal involving the OWSME, the Model martensite reorientation (i.e., achieved by the migration of twinned interfaces) is gradually converted to the Mode-II one (i.e., achieved by the nucleation and growth of martensite variants with favorable orientations) due to the influence of plastic deformation; the reverse transformation is restrained by the plastic deformation, leading to the accumulation of residual martensite phase; moreover, the twinned martensite phase is gradually transited into the re-oriented one due to the interaction among the plastic deformation, residual martensite phase and temperature-induced martensite transformation; the irreversible plastic deformation and the accumulation of residual martensite phase lead to the decrease of recoverable strain, eventually resulting in the predicted cyclic degeneration of the OWSME of NiTi SMA single crystal.