Comparison between spark plasma sintering and hot extrusion for solid-state recycling of Al-Si-Cu-Fe alloy chips

To investigate the low-cost and short-process recycling technologies for aluminium alloys, recycled chip-based Al-Si-Cu-Fe alloys were fabricated by spark plasma sintering (SPS) and hot extrusion. Microstructural observations by optical microscopy and scanning electron mi-croscopy indicated that the recycled alloys could achieve good metallurgical bonding between the chips by fragmenting the alumina films on the chip surface by spark plasma sintering and hot extrusion after hot compress. The hot extruded recycled alloy has a smaller matrix grain size and second phase size than that of spark plasma sintered recycled alloys, due to the dy-namic recrystallization and fragmentation of strong plastic deformation that occurs during the hot extrusion process. As a result, the chip-based Al-Si-Cu-Fe alloy recycled by hot extrusion after hot compress exhibited the best mechanical properties, with ultimate tensile strength, yield strength, and elongation of 258 and 132 MPa, and 8.6 % than that recycled by spark plasma sintering because of the effective metallurgical bonding between the chips, refinement of matrix grains, fragmentation and dispersion reinforcement of the oxide film and the second phase.