A comprehensive review of the recent developments in friction stir welding of metals, alloys, and polymers: a review of process parameters and properties

Friction stir welding (FSW) is a solid-state joining process of similar or dissimilar metals including thermoplastics. This technique came into practice when difficult-to-weld materials like Aluminum, Magnesium, Titanium, and other metal alloys along with polymers were not able to be joined by fusion welding. These light metals and polymers have enormous applications in areas of construction, synthesis of composites, and pipeline distribution, etc., as they possess high strength for their application at extreme conditions. Their replacement after the generation of crack or leakage led to high-cost investment. Metals and composites containing two or more similar or dissimilar elements can be sound welded by FSW considering the process parameters like tool rotation speed, welding speed, feed rate, welding tool material, and its dimensions used, etc. Although this method of joining was familiar for metals and metals alloys more specifically to aluminum, magnesium, and their alloys, its reach has now extended up to the joining of metal in form of composites in processed area and welding/processing of polymers too. The need for polymer composites has increased because of their enhancement in mechanical properties over metallic composites. Many researchers have progressively used FSW for welding/joining polymers and their composites. This review reflects the understanding of developments in FSW for the fabrication and joining of similar and dissimilar metals, metal-alloys, and polymers summarizing in terms of the effect of process parameters on properties, microstructure, strength, and efficiency.