Friction stir processing - State of the art

Increasing demands for operating properties of fabricated elements on one hand, and a necessity of reducing mass of a structure on the other, triggers materials engineering research into producing surface layers representing required functional properties. Methods commonly used in the production of surface layers, such as surfacing, spraying or re-melting with a laser beam have been known for years. A new method is the friction stir processing (FSP) of surface layers. The FSP process is primarily used for the modification of microstructure in near-surface layers of processed metallic components. In particular, the process may produce: fine grained structure, surface composite, microstructural modification of cast alloys, alloying with specific elements, improvement of welded joints quality. The chapter is composed of a few main parts. In the first part, based on literature review the main application and achievements of FSP processes are presented. In the second part: analysis of the process. The third part is focused on microstructure refinement and the last part provide information about friction stir alloying as well as friction stir processing with ultrasonic vibration.