Bimetal structures manufacturing with wire arc additive manufacturing (WAAM): review of microstructure, interface, and mechanical properties

Bimetallic structures are heterogeneous systems that combine the advantages of two different metallic materials, thereby providing tailored physical and mechanical properties for specific applications. In recent years, wire arc additive manufacturing has emerged as a promising technology for producing bimetallic structures, thanks to its high deposition rates and material efficiency. The use of wire arc additive manufacturing in the fabrication of bimetallic structures enables the production of different alloys within a single component, thereby paving the way for functionally graded and multi-material designs. The microstructures of bimetallic components produced using this method exhibit heterogeneities depending on the heat input, interlayer thermal stresses, intermetallic phase formation, and processing parameters. Mechanical properties, such as tensile strength, yield strength, and hardness, are directly dependent on the interfacial bonding conditions. At interfaces where brittle intermetallic phases form, a loss of ductility and an increased tendency to fracture are observed. A sufficient metallurgical bonding between two metallic materials results in acceptable mechanical performance in bimetallic structures built using wire arc additive manufacturing. Alloy compatibility, heat input control, and interface properties are critical for the successful application of bimetallic structures produced using this method. This review comprehensively evaluates the microstructural properties, mechanical behavior, and challenges of bimetal structures produced by wire arc additive manufacturing. The novelty of this review lies in its integrative analysis of interface-microstructural evolution and mechanical response, providing a unified perspective that has not been explicitly addressed in earlier studies. In addition, this study aims to provide a guiding framework for future research by presenting the relationship between the microstructure and mechanical properties of bimetallic structures fabricated using wire-arc additive manufacturing.