Multi scale performance breakthrough of Sc/Zr/Mn microalloying controlled wire arc additive manufacturing of high-strength light alloys

To address uneven precipitates, insufficient strength/ductility, and poor corrosion in wire arc additive manufacturing (WAAM) high-strength aluminum alloys, this study employs synergistic Sc/Zr/Mn multimicroalloying and a two-stage heat treatment. After heat treatment, grain coarsening is significantly suppressed, and only an approximately 0.7 μm increase in grain size is observed. High-density precipitation of nanoscale L12-Al3(Sc,Zr) with the η′ phase was promoted. The transverse tensile strength of the optimised material reached 522.9 MPa, and the elongation was 10.8%. The hardness increased to 195 HV0.1, which is 62.5% greater. The width of the passivation zone in the heat-treated state is extended to 0.28 V, and the self-corrosion current density is reduced by an order of magnitude. This work reveals the mechanism of Sc/Zr-induced heterogeneous nucleation and the critical role of two-stage heat treatment in controlling the precipitate distribution of high-performance WAAM Al alloys.