Superior strength-ductility synergy achieved in WA-DED Mg alloys by modulating precipitates through double-stage aging

Wire arc directed energy deposition (WA-DED) offers significant potential for rapid fabrication of large-scale Mg alloy components, yet its use is hindered by limited wire availability and strength-ductility trade-offs. Here, we present a groundbreaking advancement in WA-DED Mg-Zn-Zr alloys. Through a novel double-stage aging strategy, an exceptional strength-ductility synergy has been achieved, with the peak-aged alloy demonstrating a yield strength (YS) of ∼214 MPa, an ultimate tensile strength (UTS) of ∼341.8 MPa and an elongation (EL) of ∼21.8 %. Notably, the UTS rivals that of WA-DED Mg-rare earth alloys, while exhibiting excellent EL. The excellent properties are caused by the formation of finer and denser ${\beta }_1^{\prime }$ precipitates during aging. These coherent precipitates play a dual role: they provide significant strengthening by impeding dislocation motion, while their shearable nature prevents stress concentration and preserves ductility. This study offers a novel pathway for developing WA-DED Mg alloys with high strength and ductility.