N24A-T023 TITLE: Scalable Additive Friction Stir (AFS) for Multi-metal Deposition

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials; Sustainment

OBJECTIVE: Develop a portable or scaled-down / aircraft scale sized friction stir deposition system that is able to structurally repair spot sizes or through holes down to 0.25" in diameter on 0.125" thick aluminum, titanium, and high-strength steel.

DESCRIPTION: Rendering forging-like instead of casting-like properties, additive friction stir deposition (AFSD) is an emerging solid-state metal additive manufacturing process uniquely capable of large-scale metal additive manufacturing, cladding, and structural repair. Friction stir deposition systems are able to deposit high-quality aluminum, titanium and high-strength steel alloys, but current commercial systems as supplied by manufacturers like MELD and BOND use tool heads with a large surface area, approximately 1-1.25" in diameter [Ref 1]. This scale is useful for larger volume material deposition but is too large for the repair of most components on Navy and Marine Corps aircraft, which have small, localized damage areas of < 1". In addition, this large tool geometry requires large backing forces to support a repair, which is likely going to be excessive for thin cross-section aircraft parts, potentially leading to part deformation during deposition [Ref 2]. The currently available systems are also very large and not practical for potential remote or portable use on aircraft.

PHASE I: Develop a concept for a friction stir deposition system that can deposit aluminum, titanium, and high-strength steel in areas < 1 square inch on substrates that are 0.125" thick. Capture relevant machine parameters and deposition data to support modeling/model development; such as high-resolution time-history data of the various parameters. At minimum, establish empirical/curve-fitting formulas to enable structural applications. Prepare a report to ONR and NAWCAD on design(s) and modeling. and prepare a Phase II testing plan.

PHASE II: Construct a prototype friction stir deposition system and assess the material properties, of the deposition of aluminum 7050-T7451, Ti6-4, and AerMet 100 alloys. Assess the properties of repaired 7050-T7451, Ti6-4, and AerMet 100 substrates using feed stock of the same alloys. Provide a report that documents the design of the prototype system, results of system performance, and results of material testing for the three alloys. Provide a Phase III plan to ONR and NAWCAD for prototype evaluation. Provide a prototype friction stir deposition system to NAWCAD for evaluation.

PHASE III DUAL USE APPLICATIONS: Assemble a full friction stir deposition system and demonstrate output meeting key deposition and material parameters, to include at least full mechanical properties related to strength and fatigue. Deliver a full friction stir deposition system to NAWCAD and a comprehensive final report containing the design, deposition, and process and testing data to ONR and NAWCAD.

The development of a scalable or portable AFSD print head with multi-metal capability would be directly applicable to in-situ repair of commercial structures for aviation and other vehicle platforms alike.

REFERENCES:

1. MELD Manufacturing. www.meldmanufacturing.com
2. Yu, Hang Z. "Additive Friction Stir Deposition." Elsevier, Cambridge, MA, 2022. ISBN:978-0-12-824374-9.

KEYWORDS: Friction stir deposition, aerospace alloys, reduced scale, portable, in-situ, sustainment

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