Interface characteristics study of Al/Mg laminated composite sheets by multi-passes RHR

In order to study the effect of rolling with heated roll (RHR) on the microstructure and properties of laminated composites, Al/AZ31B/Al laminated composites were fabricated by multi-passes RHR in this paper. The influences of different reduction and annealing temperatures on the interfacial morphology and bonding properties of the composites were analyzed by OM, XRD, SEM and design mold tests. The results show that the RHR has a deformation and promoting the formation of a diffusion layer, and the discontinuous diffusion layer is formed at bonding interface of composite sheets under high reduction. With the increase of the reduction, the bonding surface gradually presents a significant “wave” type from flat, and the shear slopes occur in pairs with similar angles. The excessive reduction leads to difficulty in the coordination of the deformation process of heterogeneous materials, and the cracks appear in some areas of the decreasing direction of the magnesium layer thickness. After annealing, the Al/Mg bonding interface forms more effective metallurgical bonding. With the increase of annealing temperature, the thickness of the diffusion layer increases, and there is a delamination phenomenon. The intermetallic compounds are Al3Mg2 (β phase) and Mg17Al12 (γ phase). The peeling morphology is quasi-cleavage fracture. When the annealing temperature is too high, the sheet-shaped intermetallic compound becomes thicker, and the two metal plates will be crackled from the intermetallic compound layer. When the reduction is 60%~70% and the annealing temperature is 200℃~250℃, the bonding strength of the composite sheet by multi-passes RHR is improved.