Dependence of the microstructure, residual stresses and texture of AA 6013 friction stir welds on the welding proces

The microstructure, the residual stresses and the texture of friction stir welds of 4 mm thick samples made of a 6013 Al –Mg– Si –Cu alloy in T4 state were investigated in order to study the influence of the friction stir welding process on the material and in order to determine the influence of different welding parameters. The results of the investigations reveal the influence of the process parameters (welding speed, tool diameter and rotational speed) on the weld properties such as the microstructure, the precipitation state, the hardness, the texture and the residual stresses. The formation of the residual stresses and their distribution is explained based on an existing, simple thermal model for the friction stir welding and on a classical model for the formation of the residual stresses in conventional fusion welding.