Abstract

A longitudinally varying magnetic field (MF) was applied during cold metal transfer (CMT) welding of Al alloys. The effect of MF on the welding process, macrostructure, microstructure and properties of weld beads was studied. The results showed that the application of MF led to arc expansion and rotation, the droplet transfer frequency decreased, the droplet volume became larger, and the droplets deflected. When the coil current was between 0 and 5 A, the weld beads porosity decreased from 4.47 to 0.26%. And when the coil current was increased to 8 A, the porosity of weld beads also increased to 2.84%. MF reduced the weld depth, wetting angle and weld reinforcement, and increased weld width. With the increase of coil current, the width of primary dendrite arms decreased from 7.75 to 5.01 μm. The area occupied by the Al–Si eutectic was enlarged, and the eutectic was refined. It was also found that the MF slightly increased the hardness of the weld beads, and the hardness distribution was more uniform.

Graphic Abstract