Study of the influence of friction stir processing on tungsten inert gas welding of different aluminum alloy

Tungsten inert gas welding is the most commonly used process for joining of aluminum alloy, which are highly demanded in aerospace application. In this process coarse grain structure, micro crack and porosity was obtained due to persisting thermal conditions when the fusion zone start to solidify. The formation of these defects on the weld region will result in reduction of weld strength about to half the parent material. To avoid these defects the top surface of gas tungsten arc welding are processed using friction stir processing up to certain depth from the top of the welds. Friction stir processing destroyed the coarse grain dendritic structure in the tungsten welded joint, because of change in grains refinement and microstructure significantly improved the hardness of the friction stir processing (FSP) weld over the base metal and TIG weld. In this study, we compared the experimental result of TIG, FSW and (TIG + FSP) welded joint. Coarse grain structure was observed in TIG welding and fine grain structure was observed in FSP process. In addition very fine grain structure we observed in stir zone due to the effect of intense plastic deformation and temperature during TIG + FSP.