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

Abstract

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.