Effect of new antisymmetric arc asymmetric extrusion on microstructure and mechanical properties of magnesium alloy sheet
The traditional symmetric extrusion(SE)and the new antisymmetric arc asymmetric extrusion(ACAE)processes are designed to prepare magnesium alloy sheets.Uniaxial tensile tests are carried out at room temperature to evaluate the mechanical properties of the sheets by sampling along the extrusion direction(ED)of the sheet at 0°,45°,and 90°(transverse direction,TD).Electron back scattering diffraction(EBSD)technique is used to characterize the microstructure of magnesium alloy sheets in different processing states,the relationship between grain size and its orientation distribution and the mechanical properties of the sheet is discussed.The results show that compared with the commercial hot rolled sheet,the tensile strength(UTS)and elongation(EL)of SE sheet in ED,TD and 45°directions are improved,and the EL increases from 7.8％～10.1％of hot rolled sheets to 18.7％～22.5％of SE sheets.The yield strength(YS),tensile strength and elongation of ACAE sheet in all three directions have been improved,the yield strength is more than 179 MPa,the tensile strength is close to or more than 300 MPa,and elonga-tion is 13.6％～20.3％.On the one hand,the improvement of properties is related to the grain refinement caused by extrusion.The grain size is refined from 24.82 μm in the HR sheet to 10.14 μm in the SE sheet and 6.55 μm in the ACAE sheet.On the other hand,it is related to the texture weakening caused by extrusion,especially ACAE sheet because of the introduction of ND(normal)and TD direction strain gradient,the basal texture is significantly weakened.
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