Effect of heat treatment on the microstructure and mechanical properties of Mg-Gd-Y-Zr alloys fabricated by wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) technology is expected to be used for the fabrication of large and complex magnesium alloy components. In this work, Mg-9.54Gd-1.82Y-0.44Zr (wt.%, GW92) alloy thin-walled components were fabricated by cold metal transfer (CMT) arc in CMT-Advance mode. The microstructure of the WAAMed GW92 alloy consists of fine equiaxed ɑ-Mg grains with an average size of ∼17 μm, eutectic phases, β" phase, cubic phases, and Zr particles. The short-term high-temperature solution treatment at 525 ℃ for 25 minutes significantly reduced the content of the eutectic phase, resulting in a significant increase in elongation (EL) (13.5 ± 0.3%). The peak aging time of the solution-treated GW92 alloy at 225 ℃ for 12 h. The WAAM-T6 sample showed a significant increase in strength while maintaining good ductility, with a yield strength (YS) of 235 ± 3 MPa, ultimate tensile strength (UTS) of 360 ± 7 MPa, and elongation of 10.8 ± 1.7%. The synergistic strength and ductility properties of Mg-Gd-Y-Zr alloys fabricated by the WAAM process were significantly impacted by the short-term high-temperature solution + aging treatments to preserve the fine grain and high-density.