A predictive framework for friction stir extrusion of AA6061 powder: coupling thermomechanical evolution, bonding and hardness

Friction Stir Extrusion (FSE) is emerging as a promising solid-state manufacturing process for the consolidation of fragmented aluminum feedstock such as machining chips and powder, offering substantial energy savings over conventional remelting. Despite its growing relevance, a comprehensive understanding of how FSE process parameters affect thermomechanical evolution and final mechanical properties remains incomplete. In this study, cylindrical AA6061 extrudates of diameter 7 mm were produced by varying tool rotational speed (200–1000 rpm) and feed rate (1–4 mm/s). Vickers microhardness was measured within core and crown regions of specimens cut from the front, middle and back of each sample. A 3D finite element model was developed in Qform UK to simulate temperature, strain, strain rate and bonding evolution throughout the process, enabling quantification of the maximum extrusion temperature, radial distributions of the strain and strain rate, and die advancement required for full consolidation of particles. The final aim of this work was to establish qualitative and quantitative relationships between FSE process parameters, thermomechanical evolution and local mechanical properties of extruded wires, thereby providing a predictive tool for process design and sustainable industrial application. Finally, a composite parameter (P FSE ) was introduced to improve predictive capability, providing a quantitative basis for FSE process optimization.