Advances in Solid‐Phase Processing Techniques: Innovations, Applications, and Future Perspectives

ABSTRACT This review examines advanced solid‐phase processing (SPP) approaches that address the inherent limitations of conventional melt‐based and some solid‐phase manufacturing methods, with an emphasis on applied aspects. The discussion centers on friction‐based SPP techniques, including friction stir welding, friction extrusion, friction surfacing, and friction consolidation, along with their derivatives. Cold spray is also considered within the SPP family. At the core of these friction‐based methods is a rotating tool that imparts substantial mechanical energy, generating severe shear‐induced plastic deformation. This activates multiple deformation mechanisms, such as dislocation glide, dislocation climb, grain boundary sliding, and atomic diffusion, whose dominance depends on material type, temperature, and strain rate. Combined with dynamic recovery and recrystallization, these mechanisms drive extensive microstructural modifications. A defining advantage of SPP is its ability to impose large strains without fracture, enabled by frictional heating, which enhances local ductility, and applied normal stress, which constrains the material and suppresses cracking. Additionally, SPP techniques require a minimal spatial footprint, as the rotating tool operates without translational motion, improving process stability. With simplified optimization, primarily governed by rotation rate and feed rate, SPP methods offer scalable, energy‐efficient, and versatile solutions for advanced manufacturing applications.