Wire-arc directed energy deposition of magnesium alloys: microstructure, properties and quality optimization strategies

Magnesium alloys are widely used in industrial fields with excellent comprehensive properties. At the same time, as the lightest structural metal, magnesium alloys are expected to replace aluminum alloys and steels to achieve significant weight reduction in aircraft and automobiles. However, the current mainstream magnesium alloy processing methods usually possess the limitations of complex process flow, low material utilization and high manufacturing cost, which limit the wide application of magnesium alloys. With the advantages of high deposition rate and high process flexibility, wire-arc directed energy deposition (DED) process is promising for the fabrication of large and complex magnesium alloy components to improve manufacturing efficiency and increase material utilization. Due to the uniqueness of wire-arc DED, magnesium alloys deposited by this process have different microstructure and properties from other techniques. Therefore, this paper systematically reviews the forming characteristics of wire-arc DED magnesium alloys, summarizes the current status of research on microstructure, properties and defects in this field and presents some feasible quality optimization strategies. On this basis, the limitations of the current research are concluded and comments are provided for subsequent research. Current research has shown that wire-arc DED has the capability to deposit full equiaxed grains magnesium alloys. The future research should be focus on the development of new magnesium alloy wires, the regulation of macro morphology, microstructure and properties, the combination of auxiliary processes and the suppression of defects, in order to further improve the properties of magnesium alloy components and broaden the way for their application.