Microstructure evolution and its correlations with mechanical properties and corrosion behavior of Mg-9Gd-3Y-2Zn-0.5Zr alloy fabricated by wire-arc directed energy deposition

High-efficiency monolithic forming of large and complex components of Mg-RE (rare-earth) alloys using wire-arc additive manufacturing technology has been attracting much attention. In this work, a novel Mg-9Gd-3Y-2Y-0.5Zr (wt%, GWZ932K) alloy component was prepared via wire-arc directed energy deposition (WA-DED) technology. The microstructure, mechanical properties, and corrosion behavior of both the as-built and heat-treated samples were comprehensively analyzed. The results showed that the as-deposited alloy was mainly composed of equiaxed grains, eutectic (Mg, Zn)₃(Gd, Y) phases, stacking faults (SFs), and RE-rich phases. The specimen exhibits layered features characterized by alternating distributed coarse grains (CG) and fine grains (FG), low texture strength, and isotropic mechanical properties. After solution-aging treatment (520 °C × 8 h + 200 °C × 10 h), the eutectic phase and SFs transformed into the long-period stacking orders (LPSO) structures. The ultimate tensile strength (UTS) of 279 MPa, yield strength (YS) of 141 MPa, and elongation (EL) of 18.7 % in the TD were obtained at room temperature (RT). Grain boundary strengthening and LPSO strengthening play an essential role in enhancing alloy properties. The electrochemical test was carried out in 3.5 wt% NaCl solution revealed that the T6-treated samples exhibited enhanced corrosion resistance compared to the as-deposited samples, which could be attributed to the corrosion barrier effect of the lamellar LPSO structure and X phase.