Enhanced printability, grain refinement and strength-ductility synergy in a Sc modified Mg-Gd alloy fabricated by laser powder bed fusion

Abstract

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.