Evolution and Formation Mechanism of Interface Structure in Rolled Mg-Al Clad Sheet

Mg-Al clad sheet was prepared by hot rolling at 420 °C for 30 min and annealed at 400 °C for 2 h. The microstructure of the bonding interface of Mg-Al clad sheet before and after annealing was characterized. The results demonstrate that after hot rolling formed, a structure composed of γ -Mg 17 Al 12 phase and β -Al 3 Mg 2 phase intermetallic compound. After rolling annealing, the microstructure of the interface layer changes from fine equiaxed crystals to columnar crystals with increased size. The diffusion thickening of the interface layer leads to the reduction of the bonding strength, and the tensile fracture occurs between Al 3 Mg 2 intermetallic compounds. Through the calculation of diffusion kinetics, the bonding interface formation mechanism of Mg-Al clad sheet was constructed: Mg 17 Al 12 was formed first to reach the solid solution saturation, and then, Al 3 Mg 2 was formed. After the formation of Al 3 Mg 2 , the growth rate was increased, and finally, a stable interface layer was formed.