Use of Additive Friction Stir in Al Alloys (Powder and Solid)

Additive Friction Stir (AFS) is a novel solid-state thermo-mechanical process for deposition of metal or metal matrix composites (MMCs) used in a variety of applications across a wide spectrum of materials.  AFS allows use of solid, powder, or combinations of powder to be used as “filler” material. Filler material is forced through the hollow AFS tool and is then stirred into the substrate at a high deposition rate.  Relatively homogenous wrought microstructures with refined grains are exhibited in materials deposited by AFS. Because it is solid-state, unweldable materials may be used.  Due to its additive nature, AFS can be used for coating, repair, additive manufacturing, or joining of similar or dissimilar materials.

In this presentation, use of AFS technology with aluminum alloys will be explored.  Processing data and resulting material properties will be reviewed for the following applications:

• Creation of aluminum silicon carbide metal matrix composites with varying volume fractions
• Repair in challenging location of unweldable Aluminum 7075
• Near-net shape additively manufactured parts using Aluminum 6061
• Fabrication of parts with aluminum powders

In addition, this presentation will review experimental data indicating low residual stress in AFS fabricated parts and their substrate.  This attribute opens up design opportunities for adding features such as stiffeners afterward to reduce material cost, machine time, and labor. Use of AFS to add intersecting rib stiffeners to a fuselage frame and external features to a space frame for NASA will be presented.