Classical recycling processes for aluminum alloys include a remelting step of the collected scraps, whether new scrap (from production steps) or old scraps (end-of-life products) are considered. A new approach has been proposed, consisting in the scraps’ direct extrusion. [1,2]. This allows to bypass the remelting step, hence decreasing the energy required for recycling: producing primary Al consumes between 168 and 200 GJ/t, which goes down to 16 to 19 GJ/t for secondary Al production by remelting, when the new solid-state recycling approach divides this number by three, down to 5-6 GJ/t. This new process is thus very promising in the global warming context, where energy and CO2 emissions savings are sought. It could be applied first to new scrap, whose composition is clearly identified.

This process was implemented for the AA6060. Extrudates based on AA6060 chips were produced, and compared with extrudates based on AA6060 cast material, taken as a reference. In this presentation, the mechanical properties of the two materials will be investigated by tensile tests, followed by in-situ X ray tomography in the case of the recycled material. The results reveal that the chips-based extrudates can display some welding problems at the chips boundary, leading to a small decrease of the mechanical properties, and especially the ductility, for some solicitation directions. Building on previous results unveiling the presence of a “prior chips boundary” MgO oxide network in the microstructure [3], the mechanical results are interpreted using scanning and transmission electron microscopy, opening the way for process optimization, aiming at mitigating the formation of this oxide network, for conserved mechanical properties through recycling.

References:
[1] A.E. Tekkaya, M. Schikorra,, D. Becker, D. Biermann, N. Hammer, K. Pantke ; Journal of Materials Processing Technology, 209 (2009) 3343-3350
[2] F. Kolpak, A. Schulze, C. Dahnke, A.E. Tekkaya, Journal of Materials Processing Technology 274 (2019) 116294
[3] M. Laurent-Brocq, L. Lilensten, C. Pinot, A. Schulze, A. Duchaussoy, J. Bourgon, E. Leroy, A. E. Tekkaya; Materialia 31 (2023) 101864