| Abstract Scope |
Additive friction stir deposition is an innovative solid-state additive process that potentially addresses the quality control issues in fusion-based metal additive manufacturing via high-temperature, rapid plastic deformation. Resulting in fully dense material, this shear-driven process leads to unique dynamic phase and microstructure evolution phenomena in hierarchical and engineering alloys across multiple length scales, such as precipitate dissolution, dynamic recovery, shear-induced subgrain rotation, precipitation via heterogeneous nucleation, and shear-induced instability of inclusions. These phenomena combined can alter the static and fatigue failure mechanisms of the as-printed material, e.g., by changing the microscopic crack initiation sites, promoting intergranular failure, and enhancing the quench sensitivity. Examples using aerospace and automotive Al alloys demonstrate that with controlled shear and thermal exposure during printing, the as-printed material can exhibit tension and fatigue performance comparable to or even better than the base material, which is unmatched by fusion-based metal additive manufacturing of Al alloys. |