Additive Friction Stir for Additive Manufacturing

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.  Additive friction stir (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. 

In this presentation, the process-property relationship of an additively manufactured aluminum alloy pressure vessel will be discussed in detail. The metallographic analysis and tensile testing show that the AFS component is as dense as that of wrought alloys with exceptional through thickness properties. 

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.