Interfacial microstructures and mechanical properties of Mg/Al bimetal produced by a novel liquid-liquid compound casting process

In the present work, a novel method was proposed to produce Mg/Al bimetal using the lost foam casting (LFC) liquid-liquid compound process with a Zn interlayer, and the interfacial microstructures and mechanical properties of the Mg/Al bimetal were investigated for the first time. Obtained results reveal that a compact metallurgical interface was formed between the AZ91D magnesium alloy substrate and the A356 aluminum alloy substrate. The metallurgical interface included two reaction layers. The reaction layer adjacent to the AZ91D substrate was composed of alpha-Mg, Al5Mg11Zn4 and MgZn phases, and the reaction layer adjacent to the A356 substrate consisted of alpha-Al, Mg-32(Al, Zn)(49) and Mg2Si phases. The addition of the Zn interlayer not only prevented different liquid metals from directly mixing, but also restrained the formation of Mg-Al intermetallics. The microhardnesses of the reaction layers were much higher than those of the substrates, and the reaction layer close to the A356 substrate had the highest microhardness. The shear strength of the Mg/Al bimetal was about 10.91 MPa, and the fracture surface of the Mg/Al bimetal exhibited a brittle fracture nature.