| Abstract Scope |
Medium-entropy alloys (MEAs), including NiCoCr, offer attractive combinations of strength, toughness, and oxidation resistance for hypersonic structures, but their high cost motivates hybrid designs that bond MEAs to conventional Ni-based alloys. Joining NiCoCr to Inconel 625 is challenging for fusion welding because melting can promote brittle intermetallic formation, chemical segregation, and thermal degradation of the MEA microstructure. This work investigates vaporizing foil actuator welding (VFAW) as a high-velocity, solid-state approach for producing Inconel 625/NiCoCr MEA dissimilar impact welds. Process-microstructure-property relationships are evaluated through microscopy, chemical analysis, hardness mapping, and mechanics-based interpretation of the collision process. The welds exhibit spatial heterogeneity associated with evolving impact velocity, collision angle, jetting, localized mixing, and interfacial deformation. Characterization reveals refined interfacial microstructures, localized mixed zones, and interface-proximal hardening without the extended heat-affected regions typical of fusion processes. Guidelines are developed for processing, properties, and implementation of MEA/Ni-based alloy impact welds in demanding structural environments. |