Effect of Conventional and Pulsed TIG Welding on Microstructural and Mechanical Characteristics of AA 6082-T6 Repair Welds

Repair welding of AA 6082-T6 joints was carried out using ER 4043 filler through the TIG welding process with or without pulsed current. Microstructure and mechanical characteristics of the joints before and after repairing were investigated by examining macrostructure, microstructure, and distributions of porosity in the weld metal (WM), and by hardness, tensile, and bending tests. We observed that the welding current, phase transformations in heat-affected zone (HAZ) and porosity introduced in the WM during welding influence on its mechanical properties in sequence. The experimental results showed that the bead width and penetration as well as size of pores in the joints were mainly influenced by the welding currents. The sound joints were obtained at a welding current of 140 A with or without pulsed current when welding speed and gas flow rate were set at 20 cm & BULL;min(-1) and 15 L & BULL;min(-1), respectively. Among them, the decrease in mechanical properties of repair weld (RW) was directly related to the phase transformations in the over-ageing zone due to the double welding thermal cycles and elevated distribution of porosity in the WM. In addition, it was observed that the comparatively smaller grain size and lower porosity in WM of the RW produced by pulsed TIG welding gave a positive effect on its mechanical properties.