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The modified cold metal transfer (CMT) heat sources by adjusting the characteristic processing parameters were conducted in wire-arc additive manufacturing (WAAM) of AZ31 magnesium alloy for thin-wall component. The processing, microstructure, and mechanical behaviour were investigated. The CMT characteristic deposited a wide and shallow weld bead coupled with good wettability and low equivalent heat input was selected for CMT-WAAM process. The microstructure of thin-wall component showed obvious layer characteristics, which consisted of the deposited layers with fine columnar dendrite grains and the HAZ interlayers with coarse equiaxed grains and some pores. The thin-wall component exhibited anisotropic tensile properties with lower yield strength, higher elongation, and higher ultimate tensile strength in the deposition direction than in the build direction. CMT-WAAM component of AZ31 magnesium alloy has an accepted mechanical property compared with the as-forged and as-cast components. To improve the component strength, minimizing the softening effect of the HAZ interlayers by preventing grain coarsening and suppressing porosity is essential. [ABSTRACT FROM AUTHOR]

Abstract: The effects of antimony (Sb) on the microstructures of as-cast Mg–8Zn–4Al (ZA84) magnesium alloy were investigated by using optical microscopy, SEM, EDX, and XRD, etc. The results indicated that the microstructures of as-cast alloys containing Sb consisted of solid solution α(Mg), ternary phases τ [Mg32(Al, Zn)49] and φ (Al2Mg5Zn2), eutectic mixture phase [α(Mg)+τ], a newly formed dual phase MgZn2, and a newly formed needle-like phase Mg3Sb2. After adding Sb, the morphologies of ternary phase on the grain boundaries have been changed from quasi-continuous-net shape to uniformly dispersed particles, and the sizes of grains were decreased from 120–130μm to 50–60μm. In this experiment conditions, the optimal addition amount of Sb was 0.3wt%. Meanwhile, the microhardness of the matrix of ZA84 magnesium alloy was found to increase with the increases of Sb additions. As the phase Mg3Sb2 with high melting point and the dual phase MgZn2 were formed, the high-temperature strength of ZA84 magnesium alloy was increased. [Copyright &y& Elsevier]