The effect of gas tungsten arc welding and pulsed-gas tungsten arc welding processes\u27 parameters on the heat affected zone-softening behavior of strain-hardened Al-6.7Mg alloy

The heat affected zone (HAZ) softening behavior of strain-hardened Al-6.7Mg alloy welded by gas tungsten arc welding (GTAW) process was investigated. Increasing the heat input during welding led to formation of a wider HAZ. Moreover, the size of the precipitates was increased at higher heat inputs. Consequently, by increasing the heat input, lower strength was obtained for the welding joints. At the second stage of the study, pulsed-GTAW (PGTAW) process was employed to improve the strength of the joints. It was observed that the overall strength of the welding joints was improved and the fracture during tensile test was moved from the HAZ to the fusion zone. Moreover, the effect of duration ratio and pulse frequency was studied. For the current study, the duration ratio did not have a significant effect on the strength and microstructure of the weld, but increasing the frequency led to higher strength of the weld and finer microstructure. © 2013 Elsevier Ltd

HAZ softening behavior of strain-hardened Al-6.7Mg alloy welded by GMAW and pulsed GMAW processes

Gas metal arc welding (GMAW) process was used to weld plates of strain-hardened Al-6.7Mg alloy. It was observed that HAZ softening issue occurred extensively for the current material using the GMAW process. So, as a solution, pulsed current was employed and the plates were welded by pulsed GMAW (PGMAW) process. The effects of peak current (93, 120, 140, and 160 A) and pulse frequency (0.5, 2.0, and 5.0 Hz) on the strength of the weldments were investigated. For high peak currents (160 A), catastrophic defects were formed in the weld metal. It was observed that for the lowest pulse frequency (0.5 Hz), increasing the peak current increased the weld strength. The peak current did not change the strength for higher frequencies (2.0 and 5.0 Hz). Furthermore, increasing the frequency from 0.5 to 2.0 Hz for peak currents of 93 and 120 A led to strength improvement. For peak current of 140 A, frequency changing was ineffective. The overall enhancement in the strength of welds and reduction of HAZ softening by employing pulsed current offers a promising opportunity for further application of GMAW process with controlled heat input for welding of strain-hardened Al-6.7Mg alloy