Achieving material diversity in wire arc additive manufacturing: Leaping from alloys to composites via wire innovation

Multi-material components featuring high performance and design flexibility have attracted considerable attention, providing solutions to meet the performance demands of high-end equipment components. Achieving material diversity in additive manufacturing (AM) is a fundamental step towards manufacturing multi-material components. Wire arc additive manufacturing (WAAM), an important branch of AM technology, boasts notable advantages in the efficient and customized preparation of large-scale parts due to its high deposition efficiency and unrestricted forming size. However, achieving material diversity in WAAM, constrained by its reliance on wire-form raw materials, has emerged as a compelling challenge. Wire innovation, including multiple, stranded, and cored wires, have furnished solutions to this challenge. To this end, this review provides an overview of the current developments in WAAM via wire innovation and suggests future research directions, aiming to serve as a reference for the further advancement of WAAM. Initially, the article introduces several WAAM printing forms, their manufacturing features, printable materials and inherent manufacturing limitations, and the intermixing of metal constituents of WAAM, prior to highlighting the advantages and necessity of achieving material diversity. Subsequently, the exposition of multi-wire-arc AM demonstrates its utility in the preparation of binary or ternary alloys, inclusive of intermetallic compounds and functionally graded materials, responding adeptly to the deficiencies of conventional WAAM, which is limited to single-material printing. The merits and progression of stranded-wire-arc AM for high-entropy alloy production are synthesized and debated, especially given that creating components with multiple metal elements via multi-wire-arc AM customarily confronts the constraint of necessitating more intricate manufacturing equipment and processes. Further, the review explores the recently developed cored-wire-arc AM technology, which actualizes the manufacturing of composite materials, amalgamating metals and non-metals, to remedy the issues encountered with standard WAAM, incapable of realizing non-metallic material printing. Considering machine tools as an important means to achieve material diversity in WAAM, we expand on the current machine tool architecture and its corresponding design tools. Finally, the current research status on WAAM via wire innovation is summarized and potential future research directions are proposed.