Aluminium has two faces when it comes to sustainability. It helps saving fuel due to its low density, yet, it is a carbon-intensive metal to produce from ores. Recycling shifts this balance towards higher sustainability. This paper addresses the question how aluminium alloys can be developed, processed and optimized for performance, using higher scrap fractions. We aim at developing design guidelines for alloys with more built-in recyclability, which targets a shift from primary synthesis (reducing ores) to secondary synthesis (melting scraps). Exploring suited pathways towards Sustainability Alloy Design requires to understand and utilize how scrap-related contaminant elements act on aluminium alloys and how alloys can be designed to become upfront more scrap-compatible, for maximized use of scraps in secondary synthesis and for better compatibility when used in new alloys. This includes topics such as the influence of scrap-related contaminants on thermodynamics and kinetics of precipitation reactions as well as their mechanical and electrochemical effects; precipitation free zones around grain boundaries; precipitate dispersion and homogeneity of as-cast microstructures; shape-modification of undesired intermetallics by doping; adjustment of processing parameters for tramp-element contaminated alloys; as well as the resulting mechanical, functional and chemical properties. Translating these basic research challenges into manufacturing recipes for successful, safe and high performance products that can meet highest quality standards requires deep understanding of the basic mechanisms behind sustainable metallurgy and recycled ‘green’ alloys, establishing a new field, termed ‘Science of Dirty Alloys’.

Prof. Dr. Dierk Raabe