Friction stir spot welding of aluminum alloys: A recent review

Abstract

Abstract The application prospect of aluminum alloys in aerospace, high speed train manufacturing, shipbuilding and automotive industries is increasing and friction stir spot welding (FSSW) is adjudged to be a non-fusion and suitable joining technology for it. Conversely, friction stir spot welding has challenging attributes such as objectionable FSSW tool pin performance and short life span in mass production stage, creation of crack initiation sites like hook defect, material flow voids and probe hole, as well as restrictions on thickness of materials that can be welded. These challenges have caused a lot of tool profile innovative modifications and technological advancement in friction stir spot welding of aluminum alloys. Nevertheless, some of these vital issues are still unresolved and this notion makes FSSW an evolving solid state joining technology. A succinct view of literature on FSSW of aluminum alloys reveals that most researchers have limited their research to the characterization of microstructure and mechanical properties of aluminum welds; thus leaving a blatant research gap in post-weld tool examinations. Tool wear mechanism and void formation mechanism in FSSW processes as well as characterization of friction stir spot welded aluminum alloys are research areas that need critical examinations. Nevertheless, this publication combines the innovative and recently developed friction stir spot welding technologies of aluminum alloys and assesses their generalized process parameters; it also covers microstructural and mechanical properties of aluminum alloys available in literature. This report classifies FSSW of aluminum alloys based on three criteria namely, probe amendment, shoulder adjustment and complexity of tool movement.