Wire arc additive manufacturing of Al-6Mg alloy using variable polarity cold metal transfer arc as power source

A variable polarity cold metal transfer (VP-CMT) arc power source with different arc modes was employed in additive manufacturing Al-6Mg alloy parts. The microstructures were characterized using scanning electron microscopy with electron back-scattered diffraction. Even equiaxed grains in size of 20.6-28.5 mu m with random orientation were obtained under VP-CMT mode, while a large number of columnar grains in bigger size exist in samples under other arc modes. Tensile strength of the VP-CMT sample with a maximum of 333 MPa is higher than that of the Al-6Mg wrought alloys due to fine-grain strengthening. However, the tensile strength of the VP-CMT sample in different tensile direction was anisotropic, with a percentage of 8-27%. The comprehensive analysis of defects and grain orientation showed that the micro pores in interlayer pore region lead to the anisotropy.