A Review of Bonding Immiscible Mg/Steel Dissimilar Metals

The challenge of joining immiscible Mg/Steel dissimilar metals lies in the absence of an Fe-Mg intermetallic or Fe-Mg solid solution in an Mg-Fe system, and differences in their physical and chemical properties. Promoting interfacial reaction and regulating the composition of interface layer are beneficial for the formation of an Mg/steel interface layer and to obtain an effective Mg/steel joint. This research work focusses on the bonding of immiscible Mg/steel dissimilar metals: First, an Mg/steel interface layer was designed by controlling the composition of added alloy elements and trace elements in the base metal. Second, the Mg/steel dissimilar metals welding methods were divided into three parts—solid state welding, welding-brazing and fusion welding. The main distinctions between them were difference in interfacial temperature, thickness of interface layer, and type of compound. Third, the orientation relationships (OR) of the Mg/interface layer system and the interface layer/steel system was investigated. In this review, the effect of welding processing parameters, addition of alloy elements, base metal, and different welding methods on the joint’s performance was studied. The mechanical property, microstructure, interface layer and metallurgical reactions of the joint were also examined. The most recent progress in joining immiscible Mg/Steel dissimilar metals and future research prospects are presented at the end of the paper.