| Abstract Scope |
Development of bulk structural nanocrystalline (NC)-materials are adjudged the next frontier for lightweighting toward energy use/emission reductions. Meanwhile, NC-materials are prone to coarsening even at room-temperature; limiting their practical use. An established nanograin-stabilization method involves solute addition and their segregation to grain-boundaries (GBs) of the solvent to lower GB-excess energy. However, such GB-decorated NC materials are conventionally-developed by thin-film techniques or multi-steps power-metallurgy process requiring high-temperature consolidation. This study, for the first time, explores friction stir processing (FSP) as a single-step method to produce bulk GB-decorated NC materials with the hypothesis that FSP generates high strain/strain rates for grain refinement and sufficient heat that drives solute GB-segregation. Using Al-Mg as model solvent-solute alloy system and advanced-characterization, we found that FSP develops functionally-graded zones, including GB-segregated regions and intermetallic phases (β and γ). This work positions FSP as a scalable, sustainable strategy for producing high-strength, thermally-stable, NC-alloys for lightweight structural applications. |