On 30 September, RecAL joined the EU-funded Digi4Circular project for the symposium “Digital Enhanced Circularity in Aluminium”, with the session “Digital Twins and Scrap-Tolerant Alloy Design for Circular Aluminum” bringing together four presentations focused on alloy design, recycled feedstocks, digital modelling and material performance.
The session opened with Stefan Gneiger of AIT-LKR, whose presentation, “From Linear to Circular: Light Metal Alloys as Enablers of Low-Carbon Industry”, set out the wider challenge. Aluminium’s low weight and recyclability make it an important material for sectors such as transport, where lightweight design can reduce energy consumption. At the same time, recycling aluminium requires only a fraction of the energy of primary production, making recovery of secondary material highly attractive.
The challenge is what happens when that material is recycled.
End-of-life aluminium scrap can contain multiple alloy types and a range of impurities. During remelting, elements such as iron, copper, nickel and zinc can accumulate, affecting microstructure, mechanical performance and corrosion resistance. As Gneiger’s presentation illustrated, conventional approaches can therefore result in downcycling, with high-value materials ending up in lower-grade applications.
The poster exhibition at MSE 2026 (© RTDS Group)
RecAL’s approach is to address this problem through alloy design for recycling: rather than attempting to make increasingly complex scrap conform to existing alloy specifications, can new alloys be designed to tolerate the impurities that realistically occur in recycled feedstock?
The following presentation from Digi4Circular explored this principle using Zorba scrap for circular aluminium alloy development. The work combined composition and microstructure modelling with experimental validation to identify compositions capable of meeting demanding performance requirements. The presentation demonstrated how circular alloy design can connect the characteristics of recycled material with the processing conditions and properties required for components.
This shift—from designing for an ideal material to designing around the material actually available—is central to making higher levels of secondary aluminium technically viable.
The RecAL Consortium’s poster on LPBF (© RTDS Group)
The third presentation, “From Impurity Contents to Stress-Strain Curves of Recycled Aluminium via Digital Twin Approach and Physics-Guided Machine Learning”, brought the digital dimension of the session to the forefront. The work demonstrated a simulation workflow capable of exploring different impurity compositions and their effects on material behaviour, potentially reducing the need to physically manufacture and test every possible material variant.
A particularly interesting aspect was the use of machine learning alongside physics-based modelling. Rather than attempting to predict the complete stress-strain response directly, the machine-learning model predicts constitutive parameters that are then used within a physical material model. The approach presented at MSE achieved low prediction errors for the datasets discussed, illustrating how computational tools could accelerate the assessment of recycled alloy compositions.
For RecAL, this connects directly with the project’s broader objective of using digital technologies alongside new recycling and alloy-development technologies. RecAL is developing a digital ecosystem designed to connect actors and information across the aluminium value chain, including its planned Dataspace and aluminium hub for circularity.
STefan Gneiger from AIT-LKR Presenting at the Congress (© RTDS Group)
The final presentation moved from material composition and modelling towards fatigue behaviour and engineering reliability. Research presented by R. Wagener examined how the choice of material model influences the apparent scatter of cyclic material properties. The work showed that variability in experimental results should not automatically be interpreted as an intrinsic property of the material: the model itself can contribute to the observed scatter.
The presentation explored strain-life models, changes in apparent stiffness and the use of accumulated plastic strain and dissipated energy to describe material evolution. For recycled aluminium, such detailed understanding is particularly important when materials are intended for demanding structural applications, where reliable predictions of performance and fatigue life are essential.
Taken together, the four presentations demonstrated the breadth of the challenge facing circular aluminium: recycling technology alone is not enough. High-quality circular production also requires better alloy design, better understanding of recycled material behaviour and digital tools capable of linking composition, processing, structure and performance.
An early prototype of the RecAL Dataspace in action at CANCOM Austria (© RTDS Group)
MSE 2026 therefore offered RecAL an opportunity to position its work within a wider European research landscape—and to show how the transition from a linear to a circular aluminium economy is increasingly becoming a challenge of materials science, engineering and data as much as recycling itself. By bringing these disciplines together, projects such as RecAL and Digi4Circular are working towards a future in which recycled aluminium can remain a high-value resource rather than being progressively downcycled.
Tristan Bath (RTDS Group)
