Keyhole welding of AA2219 aluminum alloy with double-pulsed variable polarity gas tungsten arc welding

A novel ultrasonic frequency double-pulsed variable polarity gas tungsten arc welding (DP-VPTIG) process was developed in the keyhole welding of 7 mm AA2219 aluminum alloy. The stable keyhole welding process was successfully achieved through analyzing the effects of characteristic current parameters on the weld formation. In low-frequency pulse peak stage, the fully penetrated keyhole formed owing to the high penetrating arc. In low-frequency pulse base stage, the keyhole closed as the arc force sharply declined. Fully equiaxed weld zone grain structures were obtained due to the stirring effect of the double pulses. The distribution of microhardness in the welded joint was consistent with that of the microstructure. It is expected to effectively improve the welding efficiency in aluminum alloy fabrication using DP-VPTIG process.