Wire-arc directed energy deposition of high performance heat treatment free Al-6Mg-0.3Sc alloy

The release of residual stress during heat treatment of additively manufactured components could lead to significant deformation, particularly for those with thin-wall features and variable cross-sections. In this study, high performance heat treatment free Al-6Mg-0.3Sc alloy components were fabricated using the wire-arc directed energy deposition (DED) technique, achieving a yield strength of 223.0 ± 0.9 MPa, tensile strength of 408.5 ± 3.2 MPa, and elongation of 20.6 ± 1.7 %. The results indicate that compared to the CMT arc mode, the CMT + PA arc mode leads to a more pronounced bimodal microstructure, resulting in improved elongation. The mechanical property enhancement mechanism relies more on solid solution strengthening and grain boundary strengthening than on precipitation strengthening. Additionally, this study establishes for the first time a correlation between droplet transition and microstructure evolution. The research presented herein lays a theoretical foundation for wire-arc DED in the direct manufacturing of large thin-walled components without the need for heat treatment.