Additive Manufacturing: Beyond the Beam III: Friction Stir Processing
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee, TMS: Additive Manufacturing Committee
Program Organizers: Brady Butler, US Army Research Laboratory; Peeyush Nandwana, Oak Ridge National Laboratory; James Paramore, Texas A&M University; Nihan Tuncer, Desktop Metal; Markus Chmielus, University of Pittsburgh; Paul Prichard, Kennametal Inc.

Tuesday 2:30 PM
March 1, 2022
Room: 263B
Location: Anaheim Convention Center

Session Chair: Nihan Tuncer, Desktop Metal

2:30 PM Introductory Comments

2:35 PM
Overview of the Process Fundamentals Underlying Additive Friction Stir Deposition: Hang Yu¹; Hunter Rauch; Robert Griffiths; ¹Virginia Polytechnic Institute and State University
    Additive friction stir deposition leverages the principle of friction stirring in the context of additive manufacturing to enable rapid heating and deformation of metals. Compared to other solid-state metal additive manufacturing technologies, which only involve local deformation, here the plastic deformation is global: the entire feed material undergoes severe plastic deformation at elevated temperatures. As a result, additive friction stir deposition is able to produce fully-dense as-printed material with equiaxed, fine microstructures and wrought-like mechanical properties—a unique capability distinguishing it from other metal additive processes. In this presentation, I will provide an overview of the process fundamentals underlying additive friction stir deposition, with a focus on the thermal history and plastic deformation path. Multi-channel in situ monitoring is shown to unravel the correlation between the process parameters and peak temperature, whereas tracer-based X-ray computed tomography reveals the mesoscopic shape evolution, plastic strain development, and concurrent grain structure evolution.

2:55 PM
Mechanical Properties and Characterization of Solid-state Additive Manufacturing of AA6061 and AA5083: Sadie Beck¹; J. Jordon²; Paul Allison²; C. Williamson²; ¹The University of West Alabama; ²The University of Alabama
    In this study, the process-structure-property performance relationship is observed and quantified for two aluminum alloys as processed through a novel solid-state additive manufacturing process, Additive Friction Stir Deposition (AFSD). This research sought to, for the first time, elucidate the effect of thermomechanical processing on the deformation mechanisms associated with AFS-D for precipitate-hardened (6xxx series) and strain-hardened (5xxx series) aluminum alloys. AFSD material presents with a refined grain morphology. The thermo-mechanical processing of AFSD results in an exchange of strengthening mechanisms – stripping the wrought material of strength gained from tempering and strain hardening and replaces it with grain boundary strengthening. While a reduced tensile strength was observed for AA6061, AA5083 performed similarly with wrought. A post deposition heat treatment was applied to AFSD AA6061 for a full tensile strength recovery. A multistage fatigue model was calibrated for AFSD AA5083 using experimental results.

3:15 PM
Micro- and Nanostructural Evolution in AA7075 Manufactured by Additive Friction Stir Deposition: Rekha M Y¹; Dustin Avery¹; Paul G Allison¹; Brian Jordon¹; Luke N Brewer¹; ¹University of Alabama
    We are investigating the micro- and nanostructural evolution of AA7075 deposited by additive friction stir deposition (AFS-D), a solid-state additive manufacturing technique. Three conditions were considered to evaluate the AFS-D process and subsequent heat treatment on the precipitate structure of the depositions. AA7075-T651 feedstock rod was deposited by AFS-D and then subjected to a post-heat treatment procedure of solutionizing (at 490慢 for 1 hr), quenching, and aging (at 120慢 for 24 hr). Using EBSD mapping, we observed a clear grain refinement from the AFS-D process, but not significant grain growth from the post-heat treatment. STEM imaging and atom probe tomography showed that the MgZn2 phases were dissolved by the AFS-D process and that the natural aging did restore some nanophase precipitates. After full post-heat treatment, the nanophase MgZn2 precipitate structure was completely restored and resulted in full strength for the material as observed in tensile testing of heat treated material.

3:35 PM
Processing-structure-property Correlation in Additive Friction Stir Deposited Ti-6Al-4V Alloy from Recycled Metal Chips: Priyanshi Agrawal¹; Rajiv Mishra¹; Ravi Verma²; ¹University of North Texas; ²Materials and Manufacturing Tech, Boeing Research and Technology
    Additive friction stir deposition (AFSD) is a novel thermo-mechanical solid state additive manufacturing process. AFSD enables manufacturing of near net shape, fully dense components with refined equiaxed grain morphology resulting in excellent mechanical properties. AFSD has the potential to produce ingots and components/builds from recycled metals (chips/scraps/wastes from industrial machining processes or municipal recycling centers). In the present study, recycled Ti-6Al-4V alloy chips were deposited using additive friction stir deposition. Detailed microstructural and mechanical property investigation of the deposited material fosters understanding of the effect of deposition parameters on the microstructure and mechanical properties. The as-deposited microstructure was characterized by fine equiaxed prior β grains with lamellar α/β colonies inside and grain boundary α. AFSD of recycled metal provides opportunities to produce structurally sound components with reduced energy consumption as well as reducing environmental waste.