A comprehensive review of twin-wire directed energy deposition-arc (TW-DED-arc) process: An in-situ alloying based additive manufacturing approach for intermetallics

Twin-wire directed energy deposition-arc (TW-DED-arc) is a metal additive manufacturing (AM) technique that involves in-situ alloying. This approach has been under development since 2014. During this procedure, two dissimilar wires are independently introduced into a single molten arc pool to create the material according to a predetermined design by adjusting the feeding ratios of the wires. In contrast to conventional AM methods that utilize pre-alloyed powder or wire as filler materials, TW-DED-arc demonstrates enhanced applicability for producing intermetallic components attributed to its in-situ alloying and arc-deposition characteristics. To date, TW-DED-arc method has demonstrated feasibility in the fabrication of a wide range of application-valuable intermetallic alloys, including titanium aluminide, iron aluminide, and nitinol. The flexible TW feeding feature also enables the easy achievement of composition functional graded materials. In 2023, the initial titanium aluminide low-pressure turbine (LPT) blade produced from TiAl-4822 alloy using TW-DED-arc fabrication method was documented. This event marks a significant milestone for this distinctive AM technology as it transitions from laboratory settings to industrial applications. The emergence of this process not only advances research on AM of intermetallics but also provides a novel approach for the flexible fabrication of intermetallics. While further efforts are required to standardize TW-DED-arc process for producing intermetallic alloys, the ongoing research on this method has already demonstrated its validity and competitiveness. This review provides a summary of the research progress on TW-DED-arc over the past decade and identifies the current challenges to serve as a roadmap for future technical advancements.