Laser–arc hybrid additive manufacturing of high strength Mg-Gd-Y-Zr alloy by regulating multi-scale microstructure

Mg-Gd-Y-Zr alloy, a typical magnesium rare-earth (Mg-RE) alloy, is gaining popularity in lightweight and high-performance manufacturing owing to its excellent mechanical properties. However, it is extremely challenging to fabricate high-performance components with large dimensions and complex shapes because of their poor processability at room temperature. In this study, we employed laser–arc hybrid additive manufacturing (LAHAM) to fabricate Mg-6.67Gd-3.75Y-0.44Zr (wt%, GW63K) alloy. Through optimizing the solidification rate, a synergistic enhancement of microstructure and properties was achieved. The results show that increasing the solidification rate can significantly refine grains by 34% and promote the uniform distribution of the micron-sized β phase. However, excessively high solidification rates result in porosity defects and lead to the local enrichment of the micron-sized β phase. By optimizing the solidification rate, the nano-phase transforms from Mg 24 Y 5 + Mg 5 Gd to Mg 24 Y 5 + Mg 5 Gd + Mg 3 Gd, and the alloy achieves a tensile strength of 250 ± 6 MPa and an elongation of 11.6% ± 1.7%. Simulations indicate that the laser and solidification rate can effectively increase the solidification morphology parameters and regulate the flow characteristics of the liquid metal, thereby promoting grain refinement and uniform phase distribution. This study provides new insights into the underlying mechanisms of high-strength Mg-Gd-Y-Zr alloys printed using laser–arc hybrid additive manufacturing.