A Simulation Study on Material Flow and Mixing Mechanism in Dissimilar Friction Stir Welding of AA6061 and AZ31 Alloys

During dissimilar Friction Stir Welding (FSW)Friction stir welding (FSW), proper material flow and mixing processes are of critical importance for a sound joint, but its mechanismMechanisms remains unclear. In this paper, a Computational Fluid Dynamics (CFD)-based simulationSimulation method was employed to study the material flow and mixing mechanismMechanisms in dissimilar Friction Stir Welding of AA6061 and AZ31 alloys based on the numerical prediction. The predicted temperature field agrees well with the experiment. The temperature measured in the Mg on the advancing side (AS) is higher than that in Al on the retreating side (RS). During the welding process, an unsteady mixing process takes place near the welding toolTools. Two material mixing patterns during the welding process are predicted, which are shoulder-affected (SA) mixing and pin-affected (PA) mixing. The SA mixing is simple and on the macro scale which leads to the interlocking feature in the joint. By contrast, the PA mixing is more intense and results in a high-Mg-percentage mixture with Al-rich patches in the AS of the SZ.