AeroMat Keynote, Rajiv S. Mishra, University of North Texas, presents, "Friction Stir Technologies – A Continuously Expanding Impact".
The invention of friction stir welding in 1995 was heralded as the most impactful discovery in metal joining as it enabled solid-state joining of unweldable high strength aluminum alloys. As we celebrate the impact of this technology over the last 30 years, it provides an opportunity to reflect on the emergence of many friction stir technologies based on the core concept of friction stir process. The basic attributes of the process which includes intense plastic deformation at high temperature and associated microstructural refinement fostered many derivative technologies. The first evolution of this technology by Mishra et al. (1999) was given a generic name of friction stir processing. The friction stir processing broadened the scope of this solid-state technology as a microstructural refinement technique with first application to superplasticity. In this overview, the pace of evolution will be presented including the most recent variants of additive friction stir deposition (AFSD) and SolidStir additive manufacturing (AM). These solid-state additive manufacturing technologies have the highest deposit rate among all the AM technologies. In addition, being solid-state processes, these variants result in wrought microstructure and are best suited for replacement of large-scale castings and forgings. Highlights of mechanical properties using these friction stir AM processes will be presented. Both these processes are also very suitable for recycling and upcycling of metallic materials. Examples of recent progress of recycling and repair will be presented to provide guidance for emerging directions. Even after 30 years of its first application, emergence of new concepts provides exciting opportunities for continued growth of friction stir technologies.