Microstructural evolution and mechanical behavior of Mg-Li alloy fabricated by cold metal transfer wire arc additive manufacturing

A thin-walled Mg-8Li-3Al-2Zn-0.5Y alloy component was manufactured by cold metal transfer wire arc additive manufacturing (CMT-WAAM). Particular attention was given to elucidating how the intrinsic thermal history during deposition influences the microstructure evolution and the resulting mechanical performance. With increasing thermal exposure from top to bottom, the α -Mg phase gradually coarsened, while fine semi-coherent Mg 3 (Al, Zn) precipitates progressively coarsened and subsequently transformed into Li(Al, Zn) core-shell structures. This microstructural evolution resulted in pronounced mechanical heterogeneity: from the top to the bottom region, the ultimate tensile strength decreased from ∼222 MPa to ∼199 MPa, whereas the elongation concurrently improved from ∼12% to ∼17%. In situ synchrotron X-ray diffraction enabled the identification of phase-specific mechanical responses during deformation. These findings offer insights into how thermal history influences microstructural evolution and mechanical behavior, informing both microstructural regulation and performance optimization for WAAM-fabricated Mg-Li alloys.