Heterogeneous lamellar structure dominated mechanical properties optimization in ARBed Al alloy laminated metal composites

1060/7050 Al/Al laminated metal composites (LMCs) with heterogeneous lamellar structures were prepared by accumulative roll bonding (ARB), cold rolling and subsequent annealing treatment. The strengthening mechanism was investigated by microstructural characterization, mechanical property tests and in-situ fracture morphology observations. The results show that microstructural differences between the constituent layers are present in the Al/Al LMCs after various numbers of ARB cycles. Compared with rolled 2560-layered Al/Al LMCs with 37.5% and 50.0% rolling reductions, those with 62.5% rolling reductions allow for more effective improvements in the mechanical properties after annealing treatment due to their relatively high mechanical incompatibility across the interface. During tensile deformation, with the increased magnitude of incompatibility in the 2560-layered Al/Al LMC with a heterogeneous lamellar structure, the densities of the geometrically necessary dislocations (GNDs) increase to accommodate the relatively large strain gradient, resulting in considerable back stress strengthening and improved mechanical properties.