Interfacial fracture characteristics of Mg/Al composite plates with different thickness ratios by asymmetrical rolling with differential temperature rolls

In this work, Mg/Al laminated metal composites with different thickness ratios were prepared by a two-pass rolling process combining asymmetrical rolling with differential temperature rolls and isothermal symmetrical rolling. The effects of different matrix thickness on the interfacial microstructure, texture evolution, mechanical properties and interfacial fracture mechanisms of Mg/Al composite plates were systematically investigated. Results showed that the thickness ratios can induce different recrystallization degrees and deformation amounts of Mg and Al layers. This results in a strong positive correlation between the thickness of diffusion layer and the thickness ratio of plate. For thickness ratios (TR) of AZ31B/Al6061 at 2, 3 and 5, the TR5 sample had the relatively largest thickness of intermetallic compounds (IMCs) and the relatively smallest bonding strength. The thickness of diffusion layer has different effects on crack initiation and propagation, which leads to first increase and then decrease in the strength and plasticity of composite plates with increasing thickness ratios. Cracking occurs at the bond between the β (Al3Mg2) in IMCs and Al layers, which is due to the aggregation of the Mg2Si phase at this location. The distribution state of the Mg2Si phase at the interface is closely related to the thickness ratio. The Mg2Si phase at the interface of the TR3 sample is better refined and uniformly distributed, which gives it the relatively best mechanical properties.