Effect of tool face geometry on additive friction stir deposition of Al-Mg-Si alloy: Process modeling and validation in correlation with mechanical properties

Additive Friction Stir Deposition (AFSD) is a solid-state additive manufacturing process that deposits material layer by layer through shear-based plastic deformation. A critical challenge in AFSD is understanding how tool face geometry governs material flow, heat generation, and microstructure evolution, factors that directly influence the mechanical performance of the build. To address this, we propose a novel and integrated approach focused on: (i) developing high-fidelity analytical-numerical models to capture spatial variations in material flow, strain rate, and temperature; (ii) designing nature-inspired tool face geometries to actively control material flow and thermal conditions; and (iii) experimentally evaluating the influence of these geometries on microstructure and mechanical properties during AFSD of an Al-Mg-Si alloy. Three tool designs, a flat tool, a four-protrusion tool, and a vortex tool are employed to investigate how tool geometry affects process behavior. Simulations are used to predict how localized flow and heat generation can be tailored through geometry design, particularly by enhancing build direction material motion and reducing thermal losses. Tensile tests on both heat-treated and non-heat-treated samples, supported by SEM, EBSD, and TEM analyses, are used to establish the link between tool-induced strain conditions and resulting microstructural features, such as grain refinement and precipitate distribution. Overall, this study highlights the critical role of tool face geometry in modulating material flow, thermal profiles, and mechanical properties during AFSD.