Additive manufacturing of magnesium alloys provides significant lightweight advantages in aerospace applications. Mg-10Gd-Zr (G10K, wt.%) alloy exhibited promising potential for laser powder bed fusion (LPBF) application, yet it still encounters challenges related to a narrow processing window and relatively low mechanical properties. In this study, Scandium (Sc) was introduced in the pre-alloyed powder to develop the Mg-10Gd-1Sc-Zr (GSc101K, wt.%) alloy tailored for LPBF process. The results indicate that the incorporation of Sc has reduced the laser reflectivity by creating micro grooves on the surface of the GSc101K alloy powder, resulting in a significant expansion of the LPBF processing window. Furthermore, the introduction of Sc in the GSc101K alloy has led to remarkable grain refinement and noticeable weakening of texture due to preferential partitioning of Sc into the α-Mg nucleus to reduce the nucleation energy barrier. The LPBF-GSc101K alloy exhibits a superior elongation (El.) of 14%, which is primarily attributed to the refined microstructure and activation of non-basal slip systems resulting from the solid solution of Sc. After a deliberately optimized T6 heat treatment, the UTS of the GSc101K alloy reaches 395 MPa while maintaining a reasonable El. of 4%, achieving a synergistic enhancement in strength and plasticity compared to the G10K alloy. The GSc101K alloy demonstrates exceptional printability, fine and uniform microstructure, and high potential of strengthening through heat treatment, presenting a competitive option for material selection of LPBF-Mg alloys.

Mg-10Gd-Zr (G10K, wt. %) is a commonly used high-performance magnesium-rare earth alloy that has demonstrated good suitability for additive manufacturing processes. However, the formability and microstructures need to be further explored for its engineering application. This study presents a systematic and in-depth investigation of the defects, microstructural characteristics, and mechanical properties of G10K alloy fabricated by laser powder bed fusion (LPBF) as a function of processing parameters. A 3D forming space for LPBF-G10K alloy is constructed by adopting laser beam diameter as the third variant other than laser power and scanning speed. With a laser beam diameter of 120 µm, the fluctuation of the melt pool is minimized, leading to the suppression of gas porosities and balling defects, and thus the expansion of forming zone of the alloy as compared to laser beam diameters of 100 or 140 µm. LPBF-G10K alloy under the optimal processing parameter consists of a heterogeneous microstructure of coarse and fine grains. The formation of abnormal lamellar structures in the coarse grains at the middle of melt pools is attributed to the planar growth along laser scanning direction. The lamellar coarse grains provide strength in the alloy due to texture-strengthening effect, while plastic deformation is primarily accommodated by equiaxed grains. These findings are instrumental for application and future modification of the LPBF-G10K alloy.