Aluminium (Al) is a circular material that can be recycled repeatedly without losing its original properties. Currently melting the feedstock represents the most energy-intensive process in the recycling process, posing a significant energy barrier to economically recycling the metal waste. [1]. In this regard, eliminating the melting step in the recycling process would be beneficial for future sustainable recycling technologies. Friction-based processing, such as friction extrusion (FE) emerges as one of the promising technologies to overcome this challenge.

FE is a solid-state material processing that utilises a non-consumable die to produce fully consolidated extrudates in various shapes, such as wire, rods and hollow structure. During the FE process, the extrusion die rotates relative to the feedstock, while an extrusion force is applied to press the die against the feedstock. Friction between the die and the feedstock introduces severe plastic deformation and generates frictional heat, softening and consolidating the materials. No external pre-heating is required during the process, making it an energy-efficient process. FE can process feedstocks directly from a variety of charge materials, including solid billet, powder or machining waste. The ability to process the machining waste, such as machining chips, positions the FE process as a promising energy-efficient technology for recycling materials into highly engineered materials.

In this study, machining chips of Al-Cu alloy are recycled using the FE process to produce extruded wires with various diameters, down to 1.5 mm wire with extrusion ratio up to 1100. Effect of the extrusion parameters and extrusion ratio on the microstructure and mechanical properties of the extruded wire will be discussed.