Enhancing Sustainability in Aluminum Recycling: Investigating the Energy Efficiency of Friction Stir Extrusion versus Traditional Hot Extrusion

Friction Stir Extrusion is solid-state recycling process which enables the direct extrusion from waste materials, reducing energy consumption and enhancing the metallurgical quality of the extruded parts. In this study, a thorough analysis was conducted on various geometries of the extruded parts, process parameters and setups: the direct and inverse traditional hot extrusion and the Friction Stir Extrusion processes. Moreover, a comprehensive evaluation of all the components contributing to the energy demand of both the traditional hot extrusion process and the Friction Stir Extrusion was conducted. To accomplish this, the same simulation model was developed and adapted for each process, extracting the data to evaluate the energy consumption related to axial thrusts, rotational forces in Friction Stir Extrusion, and preheating in traditional extrusion. Through the comparison of the obtained results, it was possible to discern the specific geometries, setups, and parameter combinations for which Friction Stir Extrusion demonstrates superior energy efficiency in contrast to traditional extrusion and vice versa. The study’s findings suggest that the Friction Stir Extrusion offers significant advantages over traditional recycling methods, enabling the production of high-quality extruded parts with reduced energy consumption, only if some certain conditions were considered. In particular, only when comparing the same extruded mass (7 g) for both technologies, Friction Stir Extrusion proved to be significantly more energy efficient in all scenarios, as only half (for lower descent tool feed) and a quarter (for higher descent tool feed) of the specific energy of the traditional extrusion process is required to complete the process. Furthermore, the identification of optimal process parameters and setups, as well as the analysis of bonding phenomena, provides valuable insight into the effective implementation of the process in the aluminum recycling industry.