Friction Stir Spot Welding offers an introduction to friction stir spot welding (FSSW) between both similar and dissimilar metals and materials. It explains the impact of the interlayer in FSSW of different metals with regard to mechanical, metallurgical, wear, thermo-mechanical, and chemical characteristics. Emphasizing the impact of interlayer on FSSW of different metals, this book discusses the influence of the interlayer in the process as a new technique. Using aerospace and automotive structures as examples, the book explains how their components successfully employ materials like dissimilar aluminium alloys, yielding increased electrical, thermal, and mechanical characteristics. It also considers the reinforcement, effect of tool geometry, wettability, and corrosion behavior of joints. This book is intended for mechanical, materials, and manufacturing professionals, researchers, and engineers working in the field of FSSW.