Microstructure and mechanical properties of hybrid pulse VPTIG arc welding of high strength aluminum alloy

The effect of ultrasonic pulse square wave current on 2219-T87 high strength aluminum alloy welds microstructure and mechanical properties was researched based on a novel ultrafast convert hybrid pulse variable polarity TIG arc welding technology. The experimental results show that the microstructure in the weld is predominantly columnar in the case of traditional variable polarity current. The grain structures in the weld zone become finer and more equiaxed with the effect of ultrasonic pulse current. Weld tensile strength and percentage elongation are obviously improved, respectively. Weld fracture type is changed from mostly brittle to the obvious mixture of dimple and brittle. The effect of hybrid pulse current is more effective with higher pulse frequency and lower pulse current duration in a certain range. The rates of weld tensile strength and percentage elongation to base metal are 70% and 58%, respectively, under a 40 kHz ultrasonic pulse current frequency and 20% pulse duty cycle.