Improved microstructure and shear strength of the Al/steel bimetal prepared by compound casting under magnetic field

Al-7Si-Cu-Mg-Mn/steel bimetal was prepared by compound casting, and the effect of the coupled traveling and rotating magnetic field on the interface microstructure and the shear strength was investigated. The phase composition does not change after applying the magnetic field and they were η-Fe 2 Al 5, τ 1- Al 2 Fe 3 Si 3 and τ 5- Al 8 Fe 2 Si from the steel side to the Al side. The thickness of the interface layer decreases from 5.1 ± 0.9 µm to 2.7 ± 0.2 µm after applying the magnetic field. The melt flow generated by the magnetic field increases the element concentration gradient of Fe in front of the liquid-intermetallic phase interface, and the diffusion flux of Fe from the intermetallic phase to the liquid increases, which accelerates the dissolution of Al 8 Fe 2 Si and slows down its growth rate. The decreased thickness of the intermetallic compound at the interface alleviates the stress concentration at the interface during the deformation and the shear strength increases from 41 ± 7 MPa to 56 ± 2 MPa. Our findings demonstrate that the application of a magnetic field during composite casting is a feasible method to improve the microstructure and bonding strength of Al/steel bimetal.