Studies were conducted on the interfacial microstructure of a steel/liquid aluminium and its evolution during the bonding rolling process. The effects of wetting time and deformation on the diffusion layer and on the bonding strength were examined. By means of electron microscopy and electron probe analysis, it was found that the diffusion layer is mainly composed of FeAl3. For a steel temperature of 250 ℃ and an aluminium temperature of 850 ℃, the diffusion layer was formed within 3 s, and the shear strength of the samples increased after 8 to 14 s. Although the interface was not damaged, it was deformed notably. For an aluminium temperature of 750 ℃ and a wetting time of 11 to 17 s, the shear strength of the interface remained high, but the interface was obviously broken during rolling, leading to reduced bonding strength. Studies of conducted on the interfacial microstructure of a steel / liquid aluminum and its evolution during the bonding rolling process. The effects of wetting time and deformation on the diffusion layer and on the bonding strength were examined. By means of electron microscopy and electron probe analysis , it was found that the diffusion layer is mainly composed of FeAl3. For a steel temperature of 250 ℃ and an aluminum temperature of 850 ℃, the diffusion layer was formed within 3 s, and the shear strength of the specimens increased after 8 to 14 s. Although the interface was not damaged, it was deformed notably. For an aluminum temperature of 750 ° C and a wetting time of 11 to 17 s, the shear strength of the interface remained high, but the interface was obviously broken during rolling , leading to reduced bonding strength.