Microstructure and Bonding Mechanism of FeCoCrNiMn/GH4169 Dissimilar Friction Welded Joint

Superalloys and high-entropy alloys (HEAs) exhibit excellent mechanical and corrosion-resistant properties. However, studies on dissimilar welding between these two material classes remain limited. In this study, the dissimilar rotary friction welding (RFW) behavior of GH4169 superalloy and FeCoCrNiMn HEA was systematically investigated. Under optimal welding conditions, a sound joint without macroscopic defects was successfully achieved. The joint exhibited asymmetric microstructural features and could be divided into the base material (BM), thermo-mechanically affected zone (TMAZ), and weld zone (WZ). A fine-grained transition band (~ 100 μm) formed at the interface due to the adhesive-shear mechanism inherent in friction welding. Elemental diffusion occurred across the interface, leading to the formation of a diffusion layer approximately 10 μm thick. However, no intermetallic compounds were detected, attributed to the “cocktail effect” of the multicomponent alloy system. Tensile testing revealed a joint strength of 576 MPa, with fracture occurring in the HEA base material, showing ductile fracture characteristics. Microhardness profiling indicated peak hardness values in the HEA-TMAZ (HV 230) and GH4169-WZ (HV 276) regions, which were associated with grain refinement induced by dynamic recrystallization. TEM analysis confirmed that the interface consisted of a single (Fe,Ni)-based FCC solid solution structure, with nanoscale Laves phase (Fe₂Nb-type) precipitates observed at grain boundaries. These findings provide further evidence that the bonding mechanism is dominated by solid-state diffusion and dynamic recrystallization.s