This work reviews friction stir processing (FSP), which is a prominent severe plastic deformation technique used to improve materials behaviors through grain refinement. Scientists have concentrated on this technique because it is the only strengthening mechanism providing superior properties of metals and alloys without sacrificing their toughness. It was found that the aforementioned technique has the capability to provide superior properties for single-phase and multiphase materials and even for the metal matrix composites. This study has been mainly restricted to review the FSP treatment of copper and its alloys because of their vast and valuable applications.
