The evolution of dynamic recrystallization and recrystallization texture during isothermal compression of NiTi shape memory alloy

摘要

Isothermal compression tests, electron backscatter diffraction (EBSD) observations and quantitative analysis are performed to investigate the effect of process parameters on the microstructure variables (i.e. recrystallized fraction, size of austenite grain and grain boundary misorientation) during isothermal compression of NiTi shape memory alloy. And the evolution of dynamic recrystallization and recrystallization texture for this alloy is thoroughly discussed in the present study. The results show that the dynamic recovery is a dominated softening mechanism at less than 0.5 strain. As the strain increases, the discontinuous dynamic recrystallization (original grain boundary bulging and strain-induced grain boundary migration) and the subsequent continuous dynamic recrystallization (subgrain rotation) also participate in the softening of NiTi shape memory alloy, leading to a steady state of flow behavior. In the deformation end stage, the grain refinement of the austenite phase due to the effect of dynamic recrystallization improves the flow stress of NiTi shape memory alloy. The texture intensity increases significantly with increasing strain during isothermal compression of NiTi shape memory alloy, and the occurrence of dynamic recrystallization during deformation promotes the formation of a strong γ-fiber texture {111}//CA.