The Effects of Process Parameters on Aluminum Friction Stir Welded Joints

The present work deals with an experimental campaign aimed to the evaluation of mechanical proper-ties of AA6060 T6 friction stir welded joints. The butt joints obtained using two different tool geometries (standard and threaded) were performed by using different values of feed rate per unit revolution (f/S) [mm/rev], obtained by varying both feed rate (f) and tool rotating speed (S). The joints quality was evaluated in terms of ultimate tensile strength (UTS). No significant differences in mechanical properties were noticed using the two different tool geometries. On the contrary, the mechanical properties of the joints resulted to be dependent from the feed rate per unit revolution and a very low UTS was observed for high values of this parameter. Besides, a certain difference in UTS was noticed when the same f/S ratio was achieved using different combinations of process parameters. This aspect was deepened and the different thermal contribution obtained by the combination of process parameters was considered to be one of the reasons of this behavior. In order to validate this hypothesis, two 3D numerical model were set up using the FEM code Abaqus. A first model based on an Explicit Arbitrary Lagrangian-Eulerian approach resulted to be effective in force prediction. A second model was set up to study the thermal distribution