Modeling of material flow in dissimilar friction stir lap welding of aluminum and brass using coupled Eulerian and Lagrangian method

Dissimilar friction stir welding of metals is crucial in terms of inter-material mixing and the intermetallic compound formation which affects the achieving a sound joint with fine mechanical properties. In this investigation, the formation of intermetallic compounds along with the material flow during friction stir lap welding (FSLW) of aluminum and brass is studied. First, the experimental investigations were performed using SEM, EDS, and XRD to probe the chemical compositions and intermetallic formation in the stir zone (SZ). Experimental results show the presence of Al₂Cu and Al₄Cu₉ intermetallics in the SZ while are dispersed in separated zones. Moreover, to study further the material mixing, the coupled Eulerian-Lagrangian (CEL) method is employed to simulate the SZ formation during the FSLW of aluminum and brass. The model successfully predicts the SZ formation and material mixing in the Al/CuZn34 interface with penetration of Al into brass at the center and penetration of earring shape brass into Al sheet at the periphery of the SZ. Results show that two distinct zones inside the SZ could be observed, in which one is filled mostly by Al₂Cu intermetallics near the Al sheet and the other is filled mostly by Al₄Cu₉ near the brass sheet. Additionally, by increasing the tool traverse speed, the amount of inter-material mixing significantly decreases, but on the other hand, the formation of intermetallic phases, which reduces the mechanical properties of the joint, is restricted.