Influence of annealing on the interfacial structure, recrystallization behaviour, and texture evolution of hot extruded Mg/Al laminated composites

The hot extrusion process is ideal for Mg/Al laminated materials; however, there is limited research on annealing for hot extruded Mg/Al laminated composites. In this study, Mg/Al composite tubes were prepared using the direct extrusion-shear deformation (DESD) process. The morphology of the Mg/Al interface at different annealing temperatures was investigated using scanning electron microscopy (SEM). As the annealing temperature increases, the bonding layer thickens, and the number of intermetallic compounds (IMCs) increases. Most of the IMCs tend to grow in a columnar manner perpendicular to the interface bonding layer. The beta-Al3Mg2 layer is notably thicker than the gamma-Al12Mg17 layer, attributable to the lower diffusion activation energy of beta-Al3Mg2. The microstructure and texture evolution of the interfacial region were analyzed using backscattered electron diffraction (EBSD). The results show that the local average misorientation (LAM) within the Al layer is higher than that within the Mg layer, suggesting that the Al layer undergoes more significant plastic deformation and accumulates more strain energy than the Mg layer. The static recrystallization (SRX) fraction of the Mg layer is higher than that of the Al layer. However, The SRX proportion of Mg decreases with increasing annealing temperature due to secondary recrystallization. The annealing temperature significantly affects the grain orientation. As the annealing temperature increases, the deformation texture (S, Brass) of the Al layer gradually transitions to the recrystallization texture (Cube) and finally forms {123}<102> texture.