Corrosion Resistance of Friction Stir Welded AA6061 Aluminium Alloy

Present work pertains to microstructure and the corrosion behaviour of the nugget zone (NZ), thermo mechanically affected zone (TMAZ) and heat affected zone (HAZ) of friction stir welded AA6061 alloy. An attempt was made to find the influence of prior thermal temper of the alloy. Potentio-dynamic polarisation testing was used to determine the pitting corrosion resistance of the welds. Optical microscopy (OM) and transmission electron microscopy (TEM) with Energy dispersive X-ray spectroscopy studies were carried out to find the mechanism of formation of TMAZ and corrosion. Friction stir welding of this alloy resulted in fine recrystallized grains in weld nugget which has been attributed to frictional heating and plastic flow. The process also produced a softened region in the weld nugget, which may be due to the dissolution and growth of possible precipitates. Corrosion resistance of nugget zone has been found to be higher than that of TMAZ and base metal. Corrosion resistance of naturally aged (T4) alloy exhibit higher corrosion resistance than that of artificial aged (T6) alloy.