Enhanced strength-ductility synergy of Mg/Al laminate by coordinating the strain gradient of constituting layers

Mg/Al laminate with ZK60Mg and TiB₂/6061Al as constitute layers was fabricated through the porthole die co-extrusion and hot rolling. The effects of rolling and roll temperatures on the microstructure, interfacial structure, mechanical properties, and crack propagation paths were studied. The results show that the intermetallic compounds layer shows an intermittent form. The strong strain/dislocation hardening ability of Mg/Al laminate is attributed to the coupled effects of interlocking Al/β interface, strain gradient, and β layer with nanotwins and stacking faults. The complex dislocation structures such as network, loop, and array are found in the Al layer. Dislocation slip is the main deformation mode of the Al layer, while dislocation slip and dynamic recrystallization are the main deformation modes of the Mg layer. As roll temperature increases, prismatic 〈a〉 slip replaces the basal 〈a〉 slip as the most important slip mode. At a rolling temperature of 400 °C and a roll temperature of 150 °C, an optimal synergy of mechanical properties is achieved, with ultimate tensile strength, shear strength, and elongation of 262.1 MPa, 36.4 MPa, and 18.1 %, respectively. As the rolling temperature increases, the fracture mode of Mg/Al laminate changes from discontinuous plastic shrinkage to transverse and longitudinal cracks. With increasing the roll temperature, the through cracks tend to form, indicating the plasticity and bonding quality of Mg/Al laminate are effectively enhanced.