Three-Point Bending Deformation Behavior of a High Plasticity Mg–2.6Er–0.6Zr Alloy Sheet

Bending is a crucial deformation process in metal sheet forming. In this study, the microstructural evolution of a highly ductile Mg–Er–Zr alloy sheet was examined in various bending regions under different bending strains using electron backscatter diffraction and optical microscopy. The results show that the Mg–Er–Zr extruded sheet has excellent bending properties, with a failure bending strain of 39.3%, bending yield strength, and ultimate bending strength of 75.1 MPa and 250.5 MPa, respectively. The exceptional bending properties of the Mg–Er–Zr extruded sheets are primarily due to their fine grain size and the formation of rare-earth (RE) textures resulting from Er addition. Specifically, the in-grain misorientation axes (IGMA) and the twinning behaviors in various regions of the specimen during bending were thoroughly analyzed. Due to the polarity of the tensile twins and their low activation stress, a significant number of tensile twins are activated in the compression zone to regulate plastic deformation. The addition of Er weakens the basal texture of the sheet and reduces the critical resolved shear stress difference between non-basal slip and basal slip. Consequently, in the tensile zone, the basal and non-basal slips co-operate to coordinate the plastic deformation, effectively impeding crack initiation and propagation, and thereby enhancing the bending toughness of the Mg–Er–Zr sheet.