The advancement of solid-state additive manufacturing new perspective on Friction stir welding/processing (FSW/P). The process is inherently elegant, in which a specially designed tool is rotated, plunged, run through the material, and finally retreated. The current research activities focus on FSW/P of thick joints, which has a direct application in structural material of high mobility armed vehicles. In-situ monitoring, correlative microscopy, and high-throughput mechanical characterization have been adopted to disseminate the relationship between microstructure and properties.