The impact of metal inert gas welding on the corrosion and mechanical behavior of AA 6061 T6

Abstract

An attempt has been made to investigate the effects of MIG welding on the corrosion and mechanical properties of AA 6061 T6. A series of experimental techniques has been conducted to evaluate the corrosion and mechanical properties of the alloy. The corrosion media used was 3.5% (wt) NaCl. Polarization and open circuit potential tests were conducted by exposing various zones independently; therefore the reported corrosion results correspond to uncoupled condition. Different mechanical tests including tensile, torsion, and hardness were carried out; the same tests were also used for the un-welded specimens. The results show that the heat affected zone (HAZ) exhibited poor corrosion properties compared to the base metal (BM). The corrosion on both HAZ and BM was of pitting nature. More corrosion was observed on HAZ due to the thermal effects of the welding. Corrosion potential of HAZ was largely fluctuated comparing to BM with more negative peaks. The corrosion potential of the BM remained relatively steady over the whole immersion time. Welded specimens show lower mechanical properties comparing to non-welded specimens. The location of failure for welded and un-welded specimens after tensile test was found to be across the centre of the specimens. Welded tensile specimens have shown lower tensile strength. The location of the failure for welded specimens after torsion test was found predominantly along the HAZ which was attributed to the microstructural alteration that caused by the generation of heat during the welding process. Un-welded torsion specimens were failed near the centre line. Welded specimens exhibited lower torsion properties compared to the non-welded specimens with a reduction of almost 50%. The lowest hardness value was found across the weld centre.