Effects of Current Density during Electrically Assisted Friction Stir Additive Manufacturing Hole Repair of AA 7075 on a Conventional Machine

Abstract:

Of interest for military applications is the repair of damaged fastener holes on aircraft. One of the preferred repair processes, specifically for aluminum alloy 7075 (AA 7075), is friction stir additive manufacturing (FSAM) to avoid hot cracking and high residual stresses. Some of the largest challenges with this additive manufacturing process, however, are the high axial force requirement to deposit the consumable tool onto the substrate material as well as the amount of downtime necessary for repair. One possible solution is the utilization of electrical assistance during the FSAM process, since the yield strength of the alloy decreases with increasing current density when depositing bar stock. This work investigates utilizing electrically assisted friction stir technology on a conventional knee mill, which is commonly used in depots and machine shops, to showcase that repairs can be completed on commercial, commonly available equipment with decreased repair time. Varying current addresses an efficiency challenge of additive manufacturing by lowering the dwell time necessary for deposition. While higher current densities would address one of the largest concerns of FSAM – the high force requirements, the ability to repair holes using a retrofit conventional system would allow for more point-of-need applications. With the eventual application of military interest in mind, 7.95 mm (5/16”) diameter holes are drilled and repaired using FSAM via a conventional Bridgeport knee mill for use in typical machine shop locations. The material properties of AA 7075 stock material are compared to FSAM hole repairs completed with and without electricity incorporated.

• Periodical: Key Engineering Materials (Volume 1047)
• Pages: 347-358
• Online since: April 2026
• Authors: Laura L. Catalano*, Cordelia M. Norris, Elizabeth M. Mamros, John T. Roth
• Keywords: Aluminum, Electrically Assisted, Friction Stir Additive Manufacturing (FSAM), Hole Repair

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