Enhanced strength–ductility synergy in gradient-structured AZ31 magnesium alloy via activation and transfer of <c+a> dislocations

The slip transfer of dislocation directly affects the microstructure evolution and formability of gradient structure (GS) magnesium (Mg) alloys during plastic deformation and determines their mechanical properties. In this paper, the GS AZ31 Mg-alloy plate was prepared by hard plate rolling (HPR). The dislocation's activation and slip transfer behavior during 10 % tensile deformation were systematically analyzed. The results show that the gradient structure activates multiple slip modes to coordinate strain gradient and local stress state changes. Under the influence of coarse grain (CG) and c-axis tilt of grain, the fine grain (FG) region induces the activation of Pyramidal dislocation, which is difficult to activate with low Schmidt factor (m) value. In contrast, <c+a> dislocation in CG is mainly activated with a high m value. The change of local stress state and the generation of strain gradient affect the slip mode of the gradient structure, which makes the dislocation fully activated and important in releasing stress concentration. The combination of and geometrically necessary dislocation (GNDs) promotes the improvement of strain hardening capacity of gradient structures.