Abstract: The effects of SiC coating on weld seam's macro-morphology, microstructure and mechanical properties of double-electrode gas metal arc welded (DE-GMAW) 2 mm thick AZ31B magnesium alloy were investigated. The microstructure, phase and phase composition of the weld seams were observed by optical and scanning microscope, X-ray diffraction, micro hardness test and tensile tests. The results showed that the penetration and the depth/width (D/W) ratio of the weld seam increased at first and then decreased with the increasing amount of the SiC coating. The results of the XRD analysis showed that the addition of SiC could not change the types of phases in the weld seam, it contained α-Mg and β-Mg17Al12. The effects of SiC were refining grain sizes and interrupting the β-Mg17Al12 phase in the weld seam, this interruption had dispersion strengthening effect. But when the amount of SiC reached a certain value, the α-Mg grains coarsened with the increasing SiC amount and the dispersion strengthening effect of the β-Mg17Al12 phase would no longer increase. The microhardness and ultimate tensile strength of the seams increased at first and then decreased with the increasing amount of coated SiC.
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2017, Vol. 31 
