Effect of Alloying Elements on Intermetallic Formation during Friction Stir Welding of Dissimilar Metals: A Critical Review on Aluminum/Steel

The main drawback of friction stir welding (FSW) dissimilar metals is the formation of intermetallic compounds (IMCs), which are brittle and affect the strength of the joint. The formation of these compounds is inevitable due to their low enthalpy of formation; however, their emergence is an indication of metallurgical bonding between dissimilar metals. This means that the determining factors of intermetallics should be optimal to ensure the formation of the joint and, at the same time, the performance of the joint. It is known that various parameters such as welding parameters, joint configuration, and alloying elements play a crucial role in the behavior of intermetallics during FSW. This review critically analyzes the effect of different alloying elements on intermetallic formation and their implications on the mechanical properties of welded joints, with a focus on the aluminum/steel interface. The study highlights the challenges and opportunities in tuning the alloying composition to minimize the adverse effects of IMCs while maximizing the joint integrity and strength, ultimately providing guidance for future research in the field.