Effect of ultra-high frequency pulse square-wave current on 5A06 aluminum alloy HPVP-GTAW joints

Based on the novel hybrid ultra-high frequency pulse square-wave variable polarity gas tungsten arc welding (HPVP-GTAW) technique, the effect of ultra-high frequency pulse square-wave current on the microstructure and mechanical properties of 5A06 aluminum alloy joints was investigated. The experimental results show that the frequency of pulse square-wave current had an important influence on the microstructure characteristics of the resultant weld. With the pulse current frequency between 40 kHz and 60 kHz, the amount of β(Mg₂Al₃) grains increased and the softening of joints decreased, the mechanical properties of joints were improved obviously. The tensile strength and percentage elongation of the joint reached more than 93% and 80% of the base metal, respectively. While the pulse frequency was kept constant at 20 kHz, the variation of pulse current amplitude and duty cycle had not obvious influence on the weld quality.