Direct hot rolling as a solid-state recycling process for green sheets production

With the increasing demand for sustainable solutions in the recycling of aluminum alloys, solid-state recycling (SSR) offers an energy-efficient alternative by avoiding the melting phase, which typically leads to high energy consumption and material loss. This study presents a novel SSR process utilizing direct hot rolling to recycle aluminum alloy chips (EN AW-5754). The main objective is to evaluate this process's feasibility and assess the recycled sheets' mechanical and microstructural properties. Aluminum alloy chips were produced from the turning process of EN AW-AA5754 bars. The chips were compacted and subsequently heat-treated at 400°C for 2 hours. The compacted samples were then hot rolled in multiple passes, with a final cold rolling step to achieve a final thickness of 0,8 mm. Mechanical properties and microstructure were analyzed using tensile testing machine and SEM-EBSD technique. The recycled samples demonstrated mechanical properties comparable to those of reference material. SEM/EBSD analysis revealed broken oxides and a layered grain structure due to the prior chips’ boundaries. Overall, the results confirm that direct hot rolling can be a viable recycling method for aluminum alloys, offering significant energy and material savings compared to conventional processes.