Gap bridging of 6061 aluminum alloy joints welded by variable-polarity cold metal transfer.

6061 aluminum alloy joints at different gap widths were welded successfully with the same parameters (except wire offset). Bead formation, microhardness, shear strength, fracture characteristic, and forming mechanism were investigated. The results indicated that the shear strength of the joints decreased with increasing gap width. The gap width had little impact on the hardness of joints, and the fracture mode of the samples at different gap widths was ductile fracture. The wire offset and wire feeding speed had significant effects on the bead formation. The results of high-speed video and current waveform analysis showed that the variable-polarity cold metal transfer (CMT) Advance (C + A) process had better gap-bridging ability due to a lower heat input and higher deposition rate compared with the conventional CMT mode. [ABSTRACT FROM AUTHOR]