Effect of incorporating high-entropy alloy interlayer on the microstructure and mechanical properties of Mg/steel resistance spot welded joints

The composite structure of magnesium alloy and stainless steel can fully leverage the respective advantages of both materials, not only ensuring structural safety but also reducing component weight, demonstrating broad application prospects. In this experiment, a high-entropy alloy interlayer was introduced for resistance spot welding of Mg/steel dissimilar materials. The macro- and micro-morphologies of the joint interface were observed, and the interfacial microstructure characteristics were investigated using analytical methods including scanning electron microscopy (SEM) and X-ray diffraction (XRD). The influence of the high-entropy alloy interlayer on the mechanical properties of the joint was analyzed, along with the examination of fracture microstructure. The results indicate that the Mg/steel joint with FeCoNiCrMn high-entropy alloy interlayer formed a distinct and stable transition zone. The joint exhibited favorable formation without defects such as cracks or pores. The interface generated abundant chemical bonds, consisting sequentially of α-Mg, α-Mg+Mg 17 Al 12 eutectic structure, Fe 4 Al 13 compound layer (magnesium side), FeCoNiCrMn "spherical" particles, (Fe,Ni) solid solution, Fe 4 Al 13 compound layer (steel side), and α-Fe. The mechanical properties of joints with AlCrCuFeNi and FeCoNiCrMn high-entropy alloy interlayers were enhanced by approximately 24.4% and 51% respectively. Fractographic analysis revealed a ductile-brittle mixed fracture mode in the joints.