Effect of 90? route on microstructure of AZ31 magnesium alloy sheets by forging-bending repeated deformation

In this paper, a novel method of severe plastic deformation (SPD), i.e., forging-bending repeated de-formation process, was proposed to prepare AZ31 magnesium alloy sheets. The effects of the new process on the equivalent strain, flow rate, microstructure, and hardness at different passes were investigated by finite element method (FEM), electron backscatter diffraction (EBSD) and Zwick/roll hardness tester. The results showed that the effective strain and flow velocity increased with the increase of the pass. Due to the transition path, the shear deformation was sufficient at each position and the uniformity was improved. After 4 deformation passes, the refined grain size was 5.02 mu m on average. The dynamic recrystallization (DRX) mechanism in the first pass was discontinuous dynamic recrystallization (DDRX), and the interaction of twins-induced DRX and continuous dynamic recrystallization (CDRX) completed the microstructure evolution in the second pass. Meanwhile, {10-12} extension twins promoted the subsequent CDRX process by dividing coarse grains and changing grain orientation. In addition, slip-dominated pyramidal < c+a > slip was also committed to grain refinement, which can achieve high plasticity. Ultimately, the hardness of AZ31 magnesium alloy can reach 77.6HV after processing and deformation, and the grain size and high-density dislocation had significant effects on the distribution of hardness.(c) 2023 Elsevier B.V. All rights reserved.