On the role of deformation twinning in domain reorganization and grain reorientation in ferroelastic crystals

The response of ferroelastic crystals on an applied stress is considered, and a distinction is seen between the reorganization of the domain structure within a grain at low stress and the reorientation of whole grains at high stress. The procedures are modeled in the framework of defect theory, i.e., by twinning dislocations and deformation twinning. The reorganization is controlled by the motion of pre-existing twinning dislocations. Since the Peierls stress of the twinning dislocations is very small domain reorganization occurs under a very small load. The process of grain reorientation involves the nucleation of dislocations and, therefore, it requires a much higher stress. This concept is confirmed by comparison with experiments.