Effect of hot-dip Al–1Si-0.3 M (La/Sc/Yb) coating on the interface of 6061/Q345 composite plate by solid-liquid cast-rolling

To improve the interfacial bonding strength of 6061/Q345 aluminum/steel composite plates, an intermediate alloy layer was hot-dip coated on Q345 steel before solid-liquid cast-rolling. In this work, first-principles calculations together with experimental characterization were employed to investigate the influence of hot-dip Al-1Si-0.3M (La/Sc/Yb) coating on the interfacial microstructures and mechanical properties of 6061/Q345 aluminum/steel composite plates. The theoretical calculations showed that Si, Sc, La, and Yb enhanced the atomic interactions at the Al–Fe interface, thereby improving the mechanical performance of the composite plates. In particular, the co-doping of Yb and Si produced the highest interfacial binding energy of 14.59 Esep/eV, indicating excellent interfacial stability. Experimental observations further revealed that the composite plate coated with hot-dip Al-1Si-0.3Yb exhibited shear strength, tensile strength, and interfacial microhardness of 135.5 MPa, 445.5 MPa, and 430 HV, respectively. Compared with the hot-dip pure Al coating, these values increased by 164.1%, 11.4%, and 32.1%. This approach markedly strengthened the interface, which is mainly attributed to the addition of Si in the coating bath suppressing the growth of the hard and brittle Al 5 Fe 2 phase within the bonding layer of the composite plate, decreasing the thickness of the metallurgical bonding layer and thereby improving the overall strength. Furthermore, the incorporation of La/Sc/Yb elements effectively reduced the segregation of Si, facilitated a more uniform distribution of Si, and consequently enhanced the mechanical properties of the composite plate. These results provide useful insights for optimizing microstructures and improving the mechanical performance of metal layered composite materials.