Understanding the stress-induced grain boundary migration behavior in a deformed Mg alloy: the role of deformation twin and grain rotation

Abstract

Stress-induced grain boundary (GB) migration plays a crucial role in plastic deformation, influencing the microstructure and mechanical properties of polycrystalline materials. While twinning and grain rotation are important deformation modes, their impact on the GB migration of Mg alloys remains unclear. This work builds the internal relationship between deformation twins, grain rotation, and stress-induced GB migration in a deformed Mg alloy by experiments and simulations. During the uniaxial compression experiment, the GB migration mainly occurs during the $\left\{10\overline{1}2\right\}$tension twin thickening. Atomic simulations reveal that twin thickening results from the slip of interface dislocations along the basal plane (0001) under shear stress. When interface dislocations of twins are hindered by the GB, local stress concentrations lead to GB migration. A new factor I, derived from experimental results, serves as a criterion to differentiate migrated from non-migrated regions during twin thickening at the mesoscale. Grain rotation accompanied by GB migration occurs under mesoscale observations. The scalar disclinations density increases at the GB junctions due to rotation and the disclinations move with the GB migration. Local rotation associated with the formation of low-angle GBs accelerates local migration and contributes to GB serration. Crystal plasticity finite element simulations show that the additional shear stress caused by grain rotation promotes GB migration. Our findings help to understand the GB migration mechanisms of Mg alloys related to the application of Mg alloys through GB engineering.