Dissimilar friction stir lap welding of aluminum to brass: Modeling of material mixing using coupled Eulerian–Lagrangian method with experimental verifications

The intermetallic compounds formation and inter-material mixing have a critical impact on achieving a sound joint with fine mechanical properties in the case of dissimilar metal friction stir welding. In this investigation formation of intermetallic compounds as well as material flow that results in inter-material mixing during friction stir lap welding of aluminum and brass are studied. First, the 2.5-mm-thick aluminum sheet was laid on the same-thickness brass sheet and then, friction stir lap welding was applied using a tool with 4-mm pin length and 6-mm pin diameter. Next, experimental investigations were performed using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, microhardness, and tensile shear test to probe the chemical compositions and intermetallic formation in the stir zone. Moreover, the coupled Eulerian–Lagrangian method is employed to simulate the stir zone formation during the process to further study inter-material mixing. In this method, the workpiece is modeled using Eulerian formulation, while Lagrangian formulation is utilized to model the tool. The model successfully predicts the stir zone formation and inter-material mixing in the aluminum–brass interface. Results shows that by increasing tool rotational speed from 500 to 2000 r/min the amount of inter material mixing significantly increases. Therefore, to achieve a joint with the highest strength in friction stir lap welding of aluminum–brass, the rotational speed should be lowered as much as it can produce defect-free joint.