Arc shape and microstructural analysis of TIG welding with an alternating cusp-shaped magnetic field

This study compared the arc shapes and microstructures obtained from gas tungsten arc welding of AZ91 magnesium alloy for different parameters of an external alternating cusp-shaped magnetic field which was applied during the welding process; the parameters included excitation currents of 1 A to 3 A and excitation frequencies of 0 Hz-100 Hz. The experimental results showed that the tungsten inert gas (TIG) arc did not rotate under the external alternating cusp-shaped magnetic field, but its cross section was continuously elongated or flattened with the change in frequency. As the excitation current and frequency changed, the arc expanded or compressed, the weld shape and the microstructure changed. When the excitation current was 2 A and the excitation frequency 80 Hz, the arc was obviously compressed, the weld appeared smooth, the depth-to-width ratio was the largest, and the microstructure was fine-grained.