Two decades of friction stir processing–a review of advancements in composite fabrication

In comparison to the traditional reinforced composites, Friction stir processed composites have emerged to be more promising because of their better properties such as strength, hardness, ductility. To note that traditional methods have proved to interfere with the bulk properties of the material and have failed to align with the modern green globe standards and hence, Friction stir processing (FSP) has emerged in recent years for producing ex-situ and in-situ surface composites. With the increasing attention towards FSP, surface composites of alloys generated with titanium and steel are also being fabricated, which earlier was limited only to Aluminum and Magnesium alloys. Considering the growth of FSP in recent years, it appears as the appropriate time to review and enhance the quality for references and academia with the main impetus on lesser known and emerging technologies in the field. FSP is a relatively new production technique yet a lot of scholars have reported its use in the fabrication of the composites and on the optimization of its process parameters. On the contrary, the impact of FSP on various mechanical and micro-structural surface properties, highlighting the effect various process variables and the importance of tool wear are few other key points in the field which still need to be revisited. This review article attempts to fill those gaps and provide a comprehensive understanding of the technique with correlations leading to successful modeling and process optimization for defect-free and cost-effective composites.