Recycling of brass chips by sustainable friction stir extrusion

Due to the high economic and environmental benefits, researchers have considered recycling metal chips, especially for the more valuable alloys of copper, brass, aluminium, etc. Several methods have been used including casting and solid-state techniques for recycling the metal chips, wasted annually in large quantities by machining processes. This work examines the sustainability of the Friction Stir Extrusion (FSE) technique, as one of the most recently developed methods for recycling metal chips, comparing it to six different casting methods. Four sustainability indicators of economic, environmental, social, and mechanical performance are calculated and compared for the FSE and casting methods, using a multi-dimensional sustainability methodology. In terms of environmental, social, and mechanical indicators, the FSE method gained significantly the highest levels and in overall sustainability, it achieved the best score of 0.78, while the worst casting technique for recycling was 0.514. However, economically, the FSE has not yet gained a foothold in the industry and needs more attention from manufacturers, environmentally friendly craftsmen, and recycling firms side. Despite the higher investment required for the FSE process (compared to conventional casting techniques) and its lower economic feasibility, the FSE is expected to become more economically viable in the future by further research and development in its tools.