Plastic deformation and microstructural evolution in rolled Mg/Al laminated composites during tension: roles of slip, twinning, and interface effects

In this study, magnesium/aluminum laminated metal composites (Mg/Al LMCs) were fabricated via hot rolling, forming an interface characterized by element diffusion between Mg and Al. Microstructural characterization revealed slight interdiffusion of Mg and Al across the interface, accompanied by non-uniform diffusion layers of varying thickness. Pronounced microstructural heterogeneity was observed near the interface: the Mg matrix exhibited uniform equiaxed grains with a strong (0001) basal texture, whereas the Al matrix contained elongated grains with a weaker copper texture. During plastic deformation, distinct slip and twinning behaviors were identified in the two constituent matrices. The microstructure evolution and plastic deformation mechanisms of the Mg/Al LMCs at room temperature were systematically investigated using in-situ tensile testing combined with SEM-EBSD analysis. The results demonstrated that multiple twin evolution modes in the Mg matrix, such as nucleation, growth, detwinning, and variant selection, contributed to the accommodation of crystal deformation, while basal <a> slip between adjacent grains maintained strain compatibility. Plastic deformation in the Mg matrix was primarily governed by slip, which also stimulated non-basal slip within neighboring twins, thereby ensuring coordinated deformation. In the Al matrix, most grains exhibited high Schmid factors, leading to the activation of multiple slip systems within individual grains, which enhanced plastic strain accommodation and improved formability. Additionally, the pronounced microstructural mismatch between the Mg and Al matrices induced significant strain gradients across the interface, promoting the accumulation of geometrically necessary dislocations. This accumulation generated back-stress strengthening and facilitated strain coordination across the interface, ultimately contributing to the enhanced ductility of the Mg/Al laminated metal composites.