Thermomechanical modeling of friction stir welding in a Cu-DSS dissimilar joint

Thermomechanical simulation is used to predict material flow and residual stresses in joining duplex stainless steel (DSS) to a Cu-alloy by friction stir welding (FSW). The coupled Eulerian-Lagrangian (CEL) method was applied for modeling large deformation. Welding experiments are used to verify simulation results. Results indicate that DSS initially flows towards the Cu-alloy side on the top surface of the retreating side. Simulations indicate that the rotating flow zone (RFZ) is dependent on the welding parameters and has a maximum value when the rotation speed and tool offset are maximum and the travel speed is minimum. After surface flow, DSS chunks are separated and move towards the pin tip by rotation. In all the studied samples, DSS represents higher temperatures and residual stresses compared to the Cu-alloy. Longitudinal residual stress is decreased by increasing rotation speed and increased by increasing travel speed. Both speed parameters have a negligible effect on transversal residual stress. At one of the welding conditions, residual stresses are close to symmetry across the weld line. This test condition also represents optimum heat distribution and highest mechanical strength in previous findings.