Abstract:Grain scale plasticity of NiTi shape memory alloy (SMA) during uniaxial compression deformation at 400 °C was investigated through two-dimensional crystal plasticity finite element simulation and corresponding analysis based on the obtained orientation data. Stress and strain distributions of the deformed NiTi SMA samples confirm that there exhibits a heterogeneous plastic deformation at grain scale. Statistically stored dislocation (SSD) density and geometrically necessary dislocation (GND) density were further used in order to illuminate the microstructure evolution during uniaxial compression. SSD is responsible for sustaining plastic deformation and it increases along with the increase of plastic strain. GND plays an important role in accommodating compatible deformation between individual grains and thus it is correlated with the misorientation between neighboring grains, namely, a high GND density corresponds to large misorientation between grains and a low GND density corresponds to small misorientation between grains.

Key words: grain scale plasticity; NiTi shape memory alloy; crystal plasticity finite element method; plastic deformation; microstructure evolution