Effect of heat treatment on the interfacial characteristics and mechanical properties of bimetal composite

A novel bimetal composite consisting of a Mn8 medium manganese steel/ SS400 mild steel was investigated for its interfacial characteristics and mechanical properties after aging treatments from 250 to 550 °C in steps of 100 °C for 1 h. The results indicate that the width of the interface increases with rising temperature, while bonding strength decreases. The hardness of the interface near the mild steel layer reduces with increasing temperature, attributed to the preferential formation of bainitic ferrite within the bonding region. Tensile testing of the bimetal composite after heat treatment revealed that the elongation increased by 10.7, 18.0, and 15.5%, while ultimate tensile strength increased by 8.9, 8.9, and 3.3% after aging at 250, 350, and 450 °C, respectively. These enhancements are attributed to the elevated acicular ferrite content within the mild steel matrix and their uniform distribution, which effectively enhances both ductility and strength. Meanwhile, three distinct fracture modes of the interface layer are proposed: longitudinal cracks induced by excessive hardness, voids defects associated with the formation of pearlite at interface layer, and transverse cracks in all conditions. These findings reveal the intricate interplay between the interface characteristics and the mechanical properties of wear-resistant medium manganese steel and formable mild steel bimetal composite following ageing treatment, which can offer insights for their potential application in engineering equipment.