Additive Friction Stir (AFS) is a solid-state thermo-mechanical process for deposition of metal or metal matrix composites (MMCs) used for a variety of manufacturing and repair applications. Due to its additive nature, AFS can be used for coating, repair, or additive manufacturing of similar or dissimilar materials. The process principle is simple and similar to friction stir welding/processing, with the exception of the use of filler material. Filler material in the form of solid or powder is fed through a rotating tool and deposited on a substrate. The filler metal is forced to flow between the rotating AFS tool and the substrate, whereby the filler materials undergoes severe plastic deformation, dynamic recrystallization, consolidation (if powder), and deposition.
Various metal deposition processes have been used for additive manufacturing of metals over the past decade. Nonetheless, there is a need for an economically viable additive manufacturing process that can offer better mechanical properties and faster deposition. AFS is one such process wherein a wide range of solid or powder metals is deposited in solid-state.
AFS is differentiated from other additive manufacturing technologies because it is a highly scalable, open atmosphere process with a high deposition rate that offers flexibility with material sets and yields a near wrought microstructure on near net shape complex 3D structures. Multiple materials can be used to produce functionally graded products.
Since AFS is a solid-state process, the residual stress formed in the deposited components is much less than the residual stresses developed during casting or other manufacturing processes that involve melting and solidification. AFS yields a metallurgical bond between the deposited material and substrate, as well as between subsequent deposited layers. Severe plastic deformation creates a refined grain structure in deposited materials.
This time lapse shows our Additive Friction Stir process to fabricate an Aluminum 2139 rib-stiffened plate. Using solid state metal deposition reduces material cost and machining time.
Materials processed using AFS include:
Magnesium, aluminum, aluminum silicon carbide, copper, copper metal matrix composites with a wide variety of refractories, magnesium, steel, oxide dispersion strengthened steel, and ultra high strength steel. AFS is capable of fabricating components using unweldable metals.