Simultaneously improving strength and corrosion resistance of additively manufactured Mg-Gd-Zr alloy by in-situ alloying with Al

Abstract

Additive manufacturing of magnesium (Mg) alloy components with intricate geometries via laser powder bed fusion (LPBF) offers significant advantages for lightweight engineering applications. However, as a commonly issue of Mg alloys, the corrosion resistance of LPBF-Mg alloys is even worse than their cast and deformed counterparts. In-situ alloying provides a rapid pathway for composition modification tailored for the LPBF process. In this study, aluminum (Al) is introduced through in-situ alloying to prepare Mg-10Gd-xAl-Zr (GA10xK, x = 0.5, 1, 2 wt. %) alloys using blended Mg-10Gd-Zr and Mg-15Al powders. By employing a lower scanning speed during LPBF, a uniform distribution of Al throughout the as-built components is achieved. The increase in Al content leads to the progressive enhancement in grain refinement and the transformation of secondary phases from Mg₃Gd to Al₂Gd with a significant reduction in size and a notable increase in number density. These microstructural transformations yield a synchronous enhancement in strength and corrosion resistance with increasing Al content. The yield strength and ultimate tensile strength of the GA102K alloy reach 328 MPa and 350 MPa, respectively, with a minimized corrosion rate of 0.787 mm/yr., surpassing the mechanical and corrosion performance of both LPBF and semi-continuous cast G10K alloys.