An Innovative Strategy to Prepare Fine-Grained Mg-Al Alloys with a Superior Strength-Ductility Synergy Via Wire-Arc Directed Energy Deposition

Abstract

Fine grain structures are necessary in obtaining superior mechanical properties of Mg alloys fabricated by wire-arc directed energy deposition (DED), which is still challenging nowadays. In the present work, a novel strategy by the synergistic effect of arc oscillation and feeding of SiC particles (SiCps), i.e., WADED-OS, has been proposed, which is extremely effective in grain refinement of the AZ31 thin-wall component. The average grain size of the WADED-OS AZ31 thin-wall component (~19 μm) decreases by ~81% compared to the counterpart fabricated via conventional straight deposition (~102.4 μm). Introducing arc oscillation can reduce the temperature gradient in the molten pool, which promotes the transition from columnar grains to equiaxed grains. As the same time, the incorporation of SiCps can decrease the average grain size due to the heterogeneous nucleation and grain growth inhibition effects. The thin-wall component produced via the novel WADED-OS strategy exhibits a superior combination of strength and ductility, i.e., the ultimate tensile strength and elongation are 265 ± 2 MPa and 19.8 ± 2.3% along the deposition direction, respectively. This study proposes an innovative strategy for achieving wire-arc DED Mg alloy components with fine microstructures and superior mechanical properties.

Keywords: Wire-arc directed energy deposition, Magnesium alloy, SiC particle, Grain Refinement, Mechanical property