Effect of energy input on porosity, microstructure and mechanical properties of high-frequency pulsed gas tungsten arc welding with filler wire for thin 6061 aluminum components

High-frequency pulsed(HFP) gas tungsten arc welding(GTAW) has shown excellent performance in welding of aluminum alloys in recent years, which makes itself a promisingly potential technique for part manufacturing in aviation industry. However, existing researches generally focuses on the effect of a single parameter while lacks multivariable researches. Considering of the fact that gap and misalignment are inevitable in real part clamping, adaptive intelligent welding is usually used during automatic manufacturing, which means under the control of filler wire amount per length of a weld, other parameters including current, welding speed and wire feed speed during one single weld are changing according to the specific clamping situation. Therefore, the influence of specific energy input led by different welding parameters within one adaptive welding program on microstructure and mechanical property of the weld needs to be clarified. This study investigates the effect of welding heat input(ranging from 1048.3 J/mm to 825.6 J/mm within one adaptive welding program control) on the formation quality of 3.25 mm thick 6061 aluminum alloy joints fabricated by HFP-GTAW with 4043 filler wire. According to the obtained results, non-monotonic relationship between heat input and porosity, with an optimal minimum of 4.92 % achieved at an intermediate heat input of 856.8 J/mm. The 21.2 % decrease of energy input during welding process would reduce the average grain size in the weld center and adjacent to fusion line by 18.6 % and 19.4 %, respectively. The ratios between fluctuation range to minimum value in average yield and the relative ranges of yield strength and ultimate tensile strength across the tested heat inputs were 14.7 % and 12.7 %, respectively. The findings provide a general overview on how the microstructure and mechanical properties would fluctuate in an adaptively controlled HFP-GTAW fabricated aluminum alloy weld.