Synergistic enhancement of strength and ductility in wire arc additive manufactured Mg-Gd-Y-Zr alloy via Ag addition

Abstract

To overcome the strength-ductility trade-off and poor formability of high-RE magnesium alloys, Mg-13Gd-3Y-XAg-Zr (x = 0, 1, and 2 wt.%) thin walls were fabricated via wire arc additive manufacturing (WAAM), followed by subsequent solution treatment and peak-aging treatment (T6). The microstructural evolution and mechanical properties of the as-deposited, solution-treated, and T6-treated alloys were systematically investigated. The non-equilibrium rapid solidification inherent to WAAM produced equiaxed fine α-Mg grains supersaturated with Gd, Y, and Ag solutes. Ag addition progressively refined the grains and suppressed grain coarsening with increasing build height. The optimized solution treatment dissolved the eutectic phases while retaining a randomly oriented fine-grained microstructure. During aging, Ag addition accelerated the attainment of peak hardness and promoted the co-precipitation of β′ and γ′′ phases. The T6-treated alloy containing 2 wt.% Ag achieved a yield strength (YS) of 422.7 MPa, an ultimate tensile strength (UTS) of 473.6 MPa, and an elongation (EL) of 4.3%, demonstrating a synergistic enhancement in strength and ductility compared with the Ag-free alloy. This synergistic enhancement originates from WAAM-induced grain refinement coupled with Ag-promoted precipitation. By combining high material utilization with superior mechanical performance, this alloy-process strategy provides a promising pathway for manufacturing high-performance magnesium components.