| Abstract Scope |
Characterized by rapid and large shear flow at elevated temperatures, additive friction stir deposition leads to refined microstructures and forged-like properties through extreme thermomechanical processing. Despite its promise in a wide variety of critical applications, e.g., scalable additive manufacturing, additive repair, and material recycling/upcycling, most practical efforts are still limited to empirical processing tactics. Going beyond empirical processing necessitates a thorough examination of the underlying thermodynamic and kinetic aspects. In this talk, we highlight the external forcing-driven nature of additive friction stir deposition and discuss the non-equilibrium thermodynamics and unique kinetic pathways enabled by external forcing. We show peculiar kinetic phenomena observed in additive friction stir deposition, including shear-driven atomic transport, shear-induced mixing and segregation, continuous dynamic recrystallization, and unconventional phase transformation. These phenomena are mediated by the supersaturated vacancies and high density of dislocations due to rapid and intense shear, potentially enabling unprecedented material structures and properties to emerge. |