Microstructure and mechanical properties of AZ31 alloy prepared by cyclic expansion extrusion with asymmetrical extrusion cavity

The microstructure, texture evolution and mechanical properties of AZ31 magnesium alloy were investigated during the cyclic expansion extrusion with the asymmetrical extrusion cavity (CEE-AEC) process. The results show that continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) occur during the CEE-AEC process. After 3 passes, the microstructures of the deformed samples are refined, and the average grain size of the alloys in asymmetrical cavity region is 6.9 μm. The maximum intensities of the basal textures increase with the increase in the number of passes, and the basal textures are deflected during the deformation process. The basal texture of the alloys in asymmetrical cavity region is tilted by approximately ±45° from the normal direction (ND) to the extrusion direction (ED). Grain refinement strengthening and texture deflection significantly improve the comprehensive mechanical properties of the deformed alloys. After 3 passes, tensile yield strength (TYS), ultimate tensile strength (UTS) and elongation-to-failure of the alloy in the asymmetric cavity region are 146 MPa, 230 MPa and 29.7%, respectively.