Macro/micro-structure and mechanical properties of Al-6Mg-0.3Sc alloy fabricated by oscillating laser-arc hybrid additive manufacturing

Abstract

Wire-based additive manufacturing (AM) presents promising opportunities for making large components with high-price materials, such us aluminum alloys containing expensive rare earth element of scandium (Al-Sc alloy). However, wire-based AM of structurally sound and defect-free aluminum components is still challenging. In this work, an oscillating laser-arc hybrid additive manufacturing (O-LHAM) process was developed to fabricate thin-wall parts of Al-6Mg-0.3Sc alloy. To show the effect of oscillating laser beam on macro/micro-structure, porosity and mechanical properties, wire and arc additive manufacturing (WAAM) of Al-6Mg-0.3Sc alloy part was also performed for comparison. The results showed that the surface roughness of O-LHAM samples was reduced by 34.7% and the effective wall width was increased by 20% when maximum width of the wall was same with WAAM. The porosity was significantly mitigated and the microstructures was refined and homogenized due to the string effect of beam oscillating in the molten pool. The as-deposited wall of Al-Sc alloy showed an ultimate tensile strength of more than 350 MPa, reaching an exceptional level among the as-deposited aluminum alloy. The O-LHAM samples showed a higher elongation and lower anisotropy, which are resulted from the mitigated porosity and homogenized microstructure.