Revealing precipitation behavior and mechanical response of wire-arc directed energy deposited Mg-Gd-Y-Zr alloy by tailoring aging procedures

Abstract

Mg-Gd-Y-Zr alloy, as a typical magnesium rare-earth (Mg-RE) alloy, is gaining popularity in the advanced equipment manufacturing fields owing to their noticeable age-hardening properties and high specific strength. However, it is extremely challenging to prepare wrought components with large dimensions and complex shapes because of the poor room-temperature processability of Mg-Gd-Y-Zr alloy. Herein, we report a wire-arc directed energy deposited (DED) Mg-10.45Gd-2.27Y-0.52Zr (wt.%, GW102K) alloy with high RE content presenting prominent combination of strength and ductility, realized by tailored nanoprecipitates enabled by optimized heat treatment procedures. Specifically, the solution-treated sample exhibits excellent ductility with an elongation (EL) of 14.6 ± 0.1%, while the aging-treated sample at 200 ℃ for 58h achieves an ultra-high ultimate tensile strength (UTS) of 371 ± 1.5 MPa. Besides, the aging-treated sample at 250 ℃ for 16h attains a good strength-ductility synergy with an UTS of 316 ± 2.1 MPa and an EL of 8.5 ± 0.1%. Particularly, the evolution mechanisms of precipitation response induced by various aging parameters and deformation behavior caused by nanoprecipitates type were also systematically revealed. The excellent ductility resulted from coordinating localized strains facilitated by active slip activity, the ultra-high strength should be ascribed to the dense nano-β' hampering dislocation motion, while the shearable nano-β1 contributed to the good strength-ductility synergy. This work thus offers insightful understanding into the nanoprecipitates manipulation and performance tailoring for the wire-arc DED preparation of large-sized Mg-Gd-Y-Zr component with complex geometries.