Abstract: Magnesium (Mg) alloys, as the lightest metal structural material with good damping capacities, have important application prospects in realizing structural lightweight and vibration reduction. However, their engineering application is greatly limited by poor plastic formability. Wire and arc additive manufacturing (WAAM) provides a potential approach for fabricating large-scale Mg alloy components with high manufacturing flexibility. In this study, the evolution of the solidification microstructure of a WAAM-processed Mg-Al-based alloy was quantitatively analyzed based on the analytical models; then, the correlations between the solidification microstructure and mechanical properties/damping capacities were investigated. The results revealed that the WAAM-processed Mg-Al-based alloy with an equiaxed-grain-dominated microstructure displayed a simultaneous enhancement in mechanical properties and damping capacities compared to those of the cast Mg-Al-based alloy. The good combination of mechanical properties and damping capacities are mainly attributed to the weakened basal texture with a relatively high Schmid factor for basal 〈a〉 slip, the twinning-induced plasticity (TWIP) effect associated with the profuse {10-12} tensile twinning, and the relatively high dislocation density caused by the thermal stress during the WAAM process.

Key words: Wire and arc additive manufacturing, Magnesium alloy, Microstructure evolution, Mechanical properties, Damping capacities