Effect of annealing on interface microstructures and tensile properties of rolled Al/Mg/Al tri-layer clad sheets

The aim of this study was to identify the effect of post-roll annealing on the interface microstructure and tensile properties of 1060 pure Al/Mg–0.2Al–1.75Mn–0.75Ce alloy/1060 pure Al tri-layer clad sheets fabricated by a combined hot and cold rolling process. There were no interface reaction phases in the as-rolled clad sheet, and the clad sheet annealed at 200 °C for 2 h. On annealing at and above 250 °C, reaction phases of Al3Mg2 on the Al side and Al12Mg17 on the Mg side were observed to form at the interface. The thickness of interface intermetallic compounds increased markedly with increasing annealing temperature, and exhibited a linear increase with the square root of annealing time, which could be well predicted via diffusion mechanisms. With increasing annealing temperature, the ultimate tensile strength first increased from 200 °C to 250 °C, where a maximum value of about 160 MPa was achieved, then decreased. While the yield strength decreased linearly, the elongation increased significantly with increasing annealing temperature. On annealing at and below 250 °C, interface debonding was absent during the tensile tests, while partial debonding occurred via a distinctive mode of zig–zag multiple cracking or fragmentation in the intermetallic compounds in the clad sheets annealed at or above 300 °C.