B8 Model Machine
MELD, formerly known as “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, MELD 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 MELD 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. MELD is one such process wherein a wide range of solid or powder metals is deposited in solid-state.
MELD 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 MELD 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. MELD 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.
Materials processed using MELD 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. MELD is capable of fabricating components using unweldable metals.
Using solid state metal deposition reduces material cost and machining time.