Surface morphology, microstructure and mechanical properties of Al-Mg-Sc alloy thin wall produced by laser-arc hybrid additive manufacturing

The refined microstructure and enhanced mechanical properties of aluminum alloys containing Sc have attracted a great deal of attention in the recent past. In this work, a wire-based process of laser-arc hybrid additive manufacturing (LHAM) was developed and utilized to fabricate Al-Mg-Sc alloy thin wall deposits. The macro morphology, microstructural features and mechanical properties of LHAMed Al-Mg-Sc alloy were systematically investigated in comparison with wire and arc additive manufacturing (WAAM) under two processing conditions, i.e., same arc current (WAAM_SA) and same heat input (WAAM_SH). The surface quality of LHAMed deposits was significantly improved compared to that of WAAM_SA due to the stabilized effect of laser on arc behaviors. The deposits made by LHAM showed a refined and homogeneous microstructure compared to that of WAAM_SH under the condition of the same heat input, and a similar grain size with that of WAAM_SA even using a higher heat input. The microhardness results showed the LHAM had a higher and more stable microhardness distribution due to the homogeneous microstructure and less burning loss of magnesium. The as-deposited walls of LHAM and WAAM_SA showed a similar ultimate tensile strength (UTS) of more than 345 MPa for both horizontal and vertical directions, which is slightly higher than that of WAAM_SH. The as-deposited wall of LHAM also showed an exceptional elongation of about 26%, which is higher than that of both WAAM_SA and WAAM_SH samples, especially in the vertical direction, indicating less anisotropy in mechanical properties.