Effect of wire feed rate on microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloy fabricated via cold metal transfer wire-arc additive manufacturing(CMT-WAAM)

Cold Metal Transfer Wire-Artic Additive Manufacturing (CMT-WAAM) demonstrates significant potential for magnesium alloy fabrication, particularly for large-scale and geometrically complex components, owing to its low heat input, high deposition efficiency, and capability for direct complex structure production. This study systematically examines the influence of varied wire feeding rates (11, 12, 13, and 14 m/min) on the microstructural evolution and mechanical performance of Mg-Gd-Y-Zn-Zr alloy fabricated via CMT-WAAM. Crucially, heat input variations induced by different wire feeding rates were found to substantially dictate material characteristics. Microstructural characterization revealed equiaxed grain formation in the as-deposited Mg-Gd-Y-Zn-Zr alloy, with grain size exhibiting an increasing gradient along the deposition direction across all tested parameters. Phase analysis identified three primary constituents: the α-Mg matrix, β-(Mg, Zn)₃(Gd, Y) eutectic phase, and rare earth (RE)-enriched cubic phases. Notably, increased heat input correlated with expanded regions containing long-period stacking ordered (LPSO) phases. The mechanical properties of CMT-WAAM processed Mg-Gd-Y-Zn-Zr alloy surpassed those of traditionally cast Mg-RE counterparts under all tested conditions. Optimal performance was achieved at a wire feeding rate of 13 m/min, demonstrating exceptional anisotropic uniformity with ultimate tensile strengths (UTS) of 260 MPa (build direction) and 259 MPa (travel direction), yield strengths (YS) of 195 MPa and 192 MPa, and elongations (EL) of 7.95 % and 8.92 %, respectively. These findings highlight the critical role of wire feeding rate in regulating thermal dynamics and resultant material properties for CMT-WAAM processed Mg-RE alloys.