Influence of corrugated/flat rolling on microstructure and tensile property of coarse-grained AZ31–0.25Ca cast alloy

Abstract

Novel corrugated rolling technology (CR) and conventional flat rolling (FR) were employed for rolling the AZ31–0.25Ca cast alloy without prior predeformation. The impact of corrugated rolling and/or flat rolling on texture modification, microstructure evolution, and mechanical properties of the magnesium alloy during two-pass rolling was examined using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), tensile tests at ambient temperature, and ABAQUS finite element simulation analysis. The results indicate that the AZ31–0.25Ca cast alloy, after homogenization with a coarse grain structure of ∼200 μm, can endure significant plastic deformation with a 60 % total rolling reduction in both corrugated-flat rolling (CFR) and flat-flat rolling (FFR) without experiencing edge cracking. Twinning is activated dramatically except for dislocation slip during CFR, which induced high-density dislocations piling up at the twin boundaries and grain boundaries of α-Mg grains. The CFR sheet exhibited a macroheterogeneous structure attributed to the distinctive corrugated roll profile. Elevated shear strain and intensified frictional shear stress were observed at the trough, resulting in the formation of an asymmetric cross shear band in the CFR sheet. Denser deformation twins and finer recrystallized grains are present at the trough, whereas fewer and coarser ones are observed at the peak, while there is a significant texture weakening effect for corrugated rolling in contrast to the conventional flat rolling. but the stress and strain heterogeneity and asymmetric cross shear band also induce strong stress concentration and result in a premature cleavage fracture and a lower tensile property in CFR sheet compared to that of the FFR sheet.