Refill friction stir spot welding of aluminum alloys: State-of-the-art and Perspectives

Refill friction stir spot welding (RFSSW) is a solid-state spot joining method that has attracted more and more attention from academia and industry at present. RFSSW has been successfully and widely used to weld aluminum alloys, magnesium alloys and other materials. However, the flow behavior, microstructure and properties of aluminum alloy joints are not fully understood. Therefore, the relationships among welding processes, flow behavior, microstructure evolution, mechanical properties, corrosion and fatigue performance of RFSSW aluminum alloy joints are critically reviewed in this paper to provide a theoretical reference and data support for the industrial application of RFSSW. The first part analyzes the published articles on RFSSW joints indexed in the Web of Science database by using a bibliometric method. The second part briefly introduces the welding tools used in publications. The third part introduces the typical welding defects and microstructure evolution of RFSSW joints. The fourth part describes the mechanical properties and failure modes. The fifth part addresses the corrosion behavior and fatigue property of RFSSW joints. The sixth part briefly summarizes the potential applications of RFSSW technology. Finally, a summary of RFSSW joints and future studies are reported.