Effect of electromagnetic stirring on interfacial microstructure and mechanical properties of Al/Mg bimetal produced by lost foam compound casting

The Al/Mg bimetal was fabricated using a novel spiral magnetic field-assisted lost foam compound casting (LFCC) process, and the effects of electromagnetic stirring (EMS) on the interfacial microstructure and mechanical properties of the Al/Mg bimetal were investigated. The results indicated that the interface of the Al/Mg bimetal without EMS consisted of Al-Mg intermetallic compounds area (IMCs area) and Al-Mg eutectic area (E area). The Mg2Si particles exhibited a reticulated agglomeration in the IMCs area, and a continuous oxide film was present at the junction of the IMCs area and E area. During shear strength measurement, interface cracks propagated along the oxide film until interface fracture occurred, leading to lower bonding strength at the interface. With EMS applied, there was no change in the phase composition of the Al/Mg interface. The EMS facilitated the diffusion of Si elements in the interface, resulting in the refinement and dispersion of the Mg2Si particles within the IMCs area. Moreover, the Mg2Si content around the oxide film significantly increased, the oxide film remained but became discontinuous. During shear strength measurement, the interface cracks didn't propagate along the oxide film but extended from the IMCs area to the E area, as a result, the shear strength increased by 29.1% compared to the samples without EMS. The study results demonstrated that applying EMS during the lost foam casting process is a feasible method for improving the microstructure and properties of the Al/Mg bimetals.