Effects of annealing on the interfacial structures and mechanical properties of hot roll bonded Al/Mg clad sheets

In this study, Al/Mg clad sheets were successfully obtained by multi-pass hot roll bonding. The effects of annealing on the evolution of interface microstructures and mechanical properties of the clad sheets were investigated. The interface microstructures were observed via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results demonstrated that the Al/Mg clad sheets exhibited satisfactory interfacial bonding. When the annealing temperature was 250 degrees C or higher, the Al3Mg2 and Al3Mg17 phases were observed at the bonding interface. Si-(Mg2Si) and Fe-(alpha-Al8Fe2Si) particles were determined in the Al3Mg2 zone near the Al side. The grains of the Al3Mg17 and Al3Mg2 layers were columnar and rod-like. The thickness of the intermetallic phases increased linearly with the square root of the annealing time. With the increase of annealing temperature, the tensile strength of the clad sheets decreased while the elongation increased initially and subsequently decreased dramatically.