RECYCLING AND UPCYCLING METAL SCRAPS BY SOLID STATE PROCESSING

In the realm of sustainability, aluminium presents a dual perspective. On the one hand, it offers the opportunity to reduce energy consumption during the products in services and manufacturing processes due to its low mass density. On the other hand, the synthesis of aluminium from ores leads to the highest amount of greenhouse gas emissions and substantial energy consumption compared to the other popular industrial metals. This environmental impact is further compounded by the increasing population, growing demand, and several contemporary trends including manufacturing, electrification, urbanization, and transportation. Presently, aluminium production faces unprecedented sustainability challenges.Interestingly, aluminium possesses the ability for infinite recycling, with approximately 75% of historically produced aluminium still in active use. However, recycling aluminium scraps, predominantly consisting of machining chips and forming process trimming scraps, poses a notable challenge due to their high surface/volume ratio, leading to oxidation, material loss, and low energy efficiency. Addressing this, researchers propose solid-state recycling methods, which directly transform scrap metal into finished or semifinished products through plastic deformation or mechanical means, avoiding remelting and conserving energy and material.This dissertation provides a detailed analysis of recycling aluminium alloys scraps through the Friction Stir Consolidation (FSC) process— a solid-state method for recycling metal scraps, achieving chip bonding through friction stir process mechanics. The research objective was how to transform recycled product into a value added product. Particular focus has been made on highlighting existing challenges such as lower mechanical properties of recycled products and limits on key process parameters. In response to these challenges, novel process variants were introduced to mitigate quality issues, and their environmental assessment was performed. Further, FSC was employed as an upcycling technique to manufacture functionally graded materials from scraps. The formability of recycled products was evaluated and comprehensively understanding solid bonding phenomena were analysed through a combination of experimental methods and numerical simulations for potential applications at industrial scale.