Mechanism of mechanical properties enhancement in laser- arc hybrid additive manufacturing of Mg-Gd-Y-Zr alloy based on nano precipitated phase

• The laser- arc hybrid additive manufacturing (LAHAM) in Mg-Gr-Y-Zr alloy was proposed for the first time. • The influence mechanism of laser on the microstructure and mechanical properties of Mg-Gr-Y-Zr alloys was revealed. • Based on the numerical simulation, the intervational mechanism of laser on the temperature characteristics and molten pool flow characteristics during the molding process of Mg-Gr-Y-Zr alloys was revealed. In order to address the urgent demand for lightweight components in the aerospace, a laser-arc hybrid additive manufacturing (LAHAM) is innovatively applied to the Mg-Gd-Y-Zr alloy in this study. The results show that compared with wire arc additive manufacturing (WAAM), the grain size and texture strength of LAHAM were reduced by about 26% and 27% respectively. The β phase at grain boundaries are effectively mitigated. In LAHAM, the nanoscale β phase (Mg 24 (Gd,Y) 5 + Mg 5 (Gd,Y)) and β 1 phase (Mg 3 (Gd,Y)) were uniformly distributed in the grain boundary. There were only nanoscale β phase distributed around the enriched second phase in WAAM. The size and type of nanoparticles directly affect the mechanical properties of alloys. The tensile strength and yield strength of WAAM specimen were about 228 MPa, 152 MPa. Compared with WAAM, the tensile strength and yield strength of LAHAM were increased by about 12% and 15%, reaching 254 MPa and 175 MPa. The contribution of precipitation strengthening is about 42%. This study provides a new perspective for the systematic application and fabrication of Mg-Gd-Y-Zr alloy.