Study on the Influence of Nickel Plating on the Structure and Properties of Aluminum/Steel Bimetallic Bonding

Aluminum/steel bimetal combines the advantages of aluminum alloy and steel, greatly leveraging the value of various industrial fields, especially in improving engine performance and fuel economy. However, it is very difficult to prepare products with good interface bonding strength. The fundamental issue stems from the presence of an excessively thick interface layer and brittle intermetallic compounds. Therefore, this study employed a 50 μm-thick Ni interlayer to control the interface layer thickness, thereby enhancing the Al/steel interfacial bonding strength. A systematic investigation was conducted on the effects of hot dip duration on the interfacial microstructure and mechanical properties of Al/steel bimetal. The influence of hot dip duration on the microstructure and mechanical properties of aluminum/steel bimetal interface was systematically studied. The results show that the 50 μm Ni intermediate layer was used to effectively control the transition layer thickness and improve the interfacial bonding strength of aluminum steel. The thickness of the interface layer gradually increases with the increase in the hot-immersion time. The thickness of the interface layer composed of the two phases of τ₁-Al₂Fe₃Si₃ and FeAl₃ on the steel side increases first and then decreases, while the interface layer composed of the two phases of τ₅-Al₈Fe₂Si and Fe₂Al₅ on the aluminum side decreases first and then increases. When the hot dip time is 240 s, the shear strength of Al/steel bimetal with 50 μm Ni interlayer showed 75% enhancement compared to Ni-free counterparts.