TY - JOUR
T1 - Making sustainable aluminum by recycling scrap
T2 - The science of “dirty” alloys
AU - Raabe, Dierk
AU - Ponge, Dirk
AU - Uggowitzer, Peter J.
AU - Roscher, Moritz
AU - Paolantonio, Mario
AU - Liu, Chuanlai
AU - Antrekowitsch, Helmut
AU - Kozeschnik, Ernst
AU - Seidmann, David
AU - Gault, Baptiste
AU - De Geuser, Frédéric
AU - Deschamps, Alexis
AU - Hutchinson, Christopher
AU - Liu, Chunhui
AU - Li, Zhiming
AU - Prangnell, Philip
AU - Robson, Joseph
AU - Shanthraj, Pratheek
AU - Vakili, Samad
AU - Sinclair, Chad
AU - Bourgeois, Laure
AU - Pogatscher, Stefan
N1 - Publisher Copyright: © 2022 The Authors
PY - 2022/4/7
Y1 - 2022/4/7
N2 - 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.
AB - 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.
KW - Alloy design
KW - Aluminum
KW - Corrosion
KW - Precipitation
KW - Processing
KW - Properties
KW - Recycling
KW - Sustainability
KW - Thermodynamics
UR - http://www.scopus.com/inward/record.url?scp=85130182706&partnerID=8YFLogxK
U2 - 10.1016/j.pmatsci.2022.100947
DO - 10.1016/j.pmatsci.2022.100947
M3 - Review article
AN - SCOPUS:85130182706
SN - 0079-6425
VL - 128.2022
JO - Progress in materials science
JF - Progress in materials science
IS - July
M1 - 100947
ER -