Aluminum crossover alloys are an emerging class of materials designed to deliver a broad and balanced combination of mechanical strength, corrosion resistance, and formability. By blending the characteristics of traditional alloy families – 5xxx and 7xxx series alloys – they open new possibilities for high-performance applications in transportation, energy, and structural components.
This versatility also makes them attractive candidates for circular material strategies. However, increasing the recycled content of aluminium comes with a downside: it raises the levels of tramp elements such as iron (Fe) and silicon (Si), which can negatively impact alloy microstructure and downstream processing. In particular, these impurities tend to form stable intermetallic compounds that reduce formability and mechanical performance during manufacturing.
Our recent study led by Dr. Sebastian Samberger addresses this challenge by investigating how the Fe/Si ratio and cooling rate during solidification influence phase transformations and microstructure evolution in AlMgZn(Cu) crossover alloys. The ultimate goal is to enable higher recycling content without compromising industrial processability.
Transformations with big impacts
Combining thermodynamic simulations with targeted experiments, we identified two critical solid-state phase transformations during homogenization:
6-to-3 transformation:
Al6(Fe,Mn) → Al13(Fe,Mn)4
This transformation breaks down large intermetallics into smaller particles, improving their shape and distribution—ideal for rolling and forming operations.
6-to-α transformation:
Al6(Fe,Mn) → Al(Fe,Mn)Si
In contrast, this transformation often produces hard-shell/soft-core particles, which are detrimental to mechanical integrity and make further processing difficult.
Toward More Recyclable, Rollable Aluminum
These findings provide a clearer picture of how impurity-induced transformations influence the workability of aluminum crossover alloys. For alloy designers and manufacturers aiming to increase recycled content, this study offers a pathway to balance sustainability with performance. Whether through targeted impurity control, refined cooling strategies, or alloy design tuning, we now better understand how to keep aluminum both recyclable and rollable.
Read the Full Study
Samberger, Sebastian and Tunes, Matheus Araujo and Weißensteiner, Irmgard and Stemper, Lukas and Kainz, Christina and Morak, Roland and Uggowitzer, Peter and Pogatscher, Stefan, Impurity-Induced Phase Transformations in Almgzn(Cu) Crossover Alloys: Pathways to Enhance Recycling Content and Processability. Available at SSRN: https://ssrn.com/abstract=5236229 or http://dx.doi.org/10.2139/ssrn.5236229
Materials at Extremes 