Making sustainable aluminum by recycling scrap: The science of “dirty” alloys

Research output: Contribution to journalReview articlepeer-review

Authors

  • Dierk Raabe
  • Dirk Ponge
  • Moritz Roscher
  • Mario Paolantonio
  • Chuanlai Liu
  • Ernst Kozeschnik
  • David Seidmann
  • Baptiste Gault
  • Frédéric De Geuser
  • Alexis Deschamps
  • Christopher Hutchinson
  • Chunhui Liu
  • Zhiming Li
  • Philip Prangnell
  • Joseph Robson
  • Pratheek Shanthraj
  • Samad Vakili
  • Chad Sinclair
  • Laure Bourgeois

External Organisational units

  • Max-Planck-Institut für Eisenforschung GmbH
  • Institute of Materials Science and Technology
  • Northwestern University
  • Imperial College London
  • Univ. Grenoble Alpes, CNRS, Grenoble INP, SIMaP
  • Monash University
  • Central South University China
  • School of Mechanical
  • The University of British Columbia

Abstract

There are several facets of aluminum when it comes to sustainability. While it helps to save fuel due to its low density, producing it from ores is very energy-intensive. Recycling it shifts the balance towards higher sustainability, because the energy needed to melt aluminum from scrap is only about 5% of that consumed in ore reduction. The amount of aluminum available for recycling is estimated to double by 2050. This offers an opportunity to bring the metallurgical sector closer to a circular economy. A challenge is that large amounts of scrap are post-consumer scrap, containing high levels of elemental contamination. This has to be taken into account in more sustainable alloy design strategies. A “green aluminum” trend has already triggered a new trading platform for low-carbon aluminum at the London Metal Exchange (2020). The trend may lead to limits on the use of less-sustainable materials in future products. The shift from primary synthesis (ore reduction) to secondary synthesis (scrap melting) requires to gain better understanding of how multiple scrap-related contaminant elements act on aluminum alloys and how future alloys can be designed upfront to become scrap-compatible and composition-tolerant. The paper therefore discusses the influence of scrap-related impurities on the thermodynamics and kinetics of precipitation reactions and their mechanical and electrochemical effects; impurity effects on precipitation-free zones around grain boundaries; their effects on casting microstructures; and the possibilities presented by adjusting processing parameters and the associated mechanical, functional and chemical properties. The objective is to foster the design and production of aluminum alloys with the highest possible scrap fractions, using even low-quality scrap and scrap types which match only a few target alloys when recycled.

Details

Original languageEnglish
Article number100947
Number of pages150
JournalProgress in materials science
Volume128.2022
Issue numberJuly
DOIs
Publication statusE-pub ahead of print - 7 Apr 2022