Metal Matrix Composites by Friction Stir Processing discusses the capabilities of utilizing friction stir processing (FSP) as a tool to manufacture new materials, such as composites. FSP is considered a tool for grain refinement. However, this work illustrates how FSP has a wider capability due to the material flow and mixing the process offers. This book highlights such aspects by demonstrating the ability of the process to incorporate a second phase and make metal matrix composites (MMCs). The book covers the current research on processing MMCs by FSP, and presents a novel approach of making ductile MMCs by FSP using metal particle reinforcements.