Investigation of microstructure and mechanical properties of GWZ1031K alloy additively manufactured by cold metal transfer-based wire-arc directed energy deposition

Wire-arc directed energy deposition (WA-DED) is a crucial additive manufacturing preparation technique for large-scale parts. Mg-Gd-Y-Zn-Zr alloys are a type of promising weight-saving structural materials. Consequently, Mg-Gd-Y-Zn-Zr alloys manufactured by WA-DED are gaining popularity for their lightweight applications in the aerospace industry. This study examined the mechanical properties and microstructural evolution of GWZ1031K alloy, which was prepared via WA-DED, both before and after heat treatment. With an average grain size of 11.1 ± 5.1 µm, as-deposited GWZ1031K alloy exhibits an inhomogeneous equiaxed grain structure, primarily composed of the α-Mg and (Mg, Zn)₃(Gd, Y) eutectic. Following heat treatment, the long-period stacking ordered (LPSO) phase and α-Mg make up the majority of the GWZ1031K alloy. The alloy exhibited a notable increase in ductility and a minor increase in strength after solid solution treatment at 500°C for 1 h. The LPSO phase precipitated out of the grain boundaries (GBs) into the grain interiors (GIs), whereas the (Mg, Zn)₃(Gd, Y) eutectic dissolved into the matrix. In addition to the pre-existing RE-rich cubic phase, the LPSO phase also inhibits grain development at GBs. Furthermore, during a 72-hour ageing treatment at 200°C, the GI produced a high-density nanoscale β′ phase, which markedly enhanced strength. With an elongation of 2.13 ± 0.6 %, the alloys demonstrated an outstanding yield strength (YS) of 263 ± 5 MPa and ultimate tensile strength (UTS) of 342 ± 10 MPa. An in-depth investigation of the microstructure and mechanical properties of the alloy under the WA-DED process can help optimize the manufacturing process parameters and provide key technical support for the large-scale production of high-performance magnesium alloy components.