Aluminium foam: swarf instead of virgin powder
in brief
Aluminium is regarded as a key material for sustainable mobility and resource-efficient products. However, its production is energy-intensive. Researchers at Fraunhofer IWU are demonstrating how production residues, aluminium swarf and end-of-life aluminium foam components can be specifically reintroduced into the manufacturing process.
Recycled materials for aluminium foam
Aluminium foam is one of the lightest structural materials. Due to its low density, high energy absorption capacity and good damping properties, it is suitable for applications in, amongst others, vehicle manufacturing, machine structures, the construction industry and energy-efficient lightweight construction systems.
Today, it is predominantly manufactured using aluminium alloy powders. The production of these powders is comparatively labour-intensive and costly. This is precisely where the research at the Fraunhofer Institute for Machine Tools and Forming Technology (IWU) comes in: production residues, aluminium swarf and end-of-life aluminium foam components are to be not only recycled, but specifically reintroduced into powder metallurgical foam production.
The focus is on single-grade aluminium swarf, production residues and end-of-life materials. These are mechanically processed and made usable as raw material for new aluminium foams. This creates an approach that can reduce the use of primary material and open up new avenues for circular production.
Recycled chips replace new powder
A particularly promising approach involves replacing energy-intensive aluminium alloy powder, either partially or completely, with recycled aluminium chips. Grinding and classifying the swarf produces a powdered raw material that can be processed into foamable semi-finished products.
The foams produced from this achieve structures and densities comparable to those of conventionally manufactured aluminium foams. The research thus demonstrates that aluminium swarf need not be regarded merely as a waste product, but can be utilised as a technically viable material for new lightweight structures.
“The use of production waste directly within the material cycle offers considerable environmental and economic potential,” explains Dr Jörg Hohlfeld, Head of the Metal Foam Group at Fraunhofer IWU. Energy consumption is particularly relevant here: significantly less energy is required to produce secondary aluminium than primary aluminium. This allows both material costs and CO₂ emissions to be reduced.
From waste to functional material
In addition to aluminium shavings, Fraunhofer IWU also investigated larger aluminium scraps. These include foils, coils – that is, offcuts from large rolls of aluminium sheet – and wheel rim material. Through multi-stage mechanical processes such as cutting, crushing, grinding and screening, defined particle sizes can be produced from these materials for foam production.
In principle, end-of-life aluminium foam components can also be reintegrated into the material cycle. To this end, the research team developed strategies for shredding, sorting and further processing in line with the material’s properties.
It is crucial that recycling is not limited to simple remelting. The Fraunhofer IWU is pursuing approaches based on solid-state recycling. This preserves large parts of the existing material structure. This can save additional energy and prevent material loss.
New perspectives for the circular economy in lightweight construction
The results show that aluminium scrap in powder form can be used as a technically equivalent alternative to newly produced aluminium alloy powder. This brings us closer to a more resource-efficient production of aluminium foams.
This approach is particularly relevant for sectors with high lightweight construction requirements. These include the automotive, mechanical engineering and railway sectors. In these sectors, aluminium foams can help to develop structures that are both lightweight and functional. If production relies more heavily on recycled materials, lightweight construction and resource efficiency can be more closely linked.
Work is to continue with a view to industrial implementation. Future research projects will focus in particular on stabilising material properties in the face of fluctuating scrap quality. In addition, comprehensive life-cycle analyses are intended to quantitatively demonstrate the environmental benefits of scrap-based foam production and prepare the technology for wider industrial application.
Key facts at a glance:
- The Fraunhofer IWU is investigating new circular pathways for the production of aluminium foam.
- Recycled aluminium swarf can partially or completely replace energy-intensive aluminium alloy powder.
- Solid-state recycling can help to save energy and prevent material losses.
- The research is particularly relevant for lightweight construction applications in the automotive, mechanical engineering and railway sectors.
FAQ
Recycled aluminium swarf can serve as a powdered raw material for foamable semi-finished products. This allows new aluminium alloy powder to be partially or completely replaced.
In solid-state recycling, material is recycled without being completely remelted. Large parts of the existing material structure are retained, which saves energy and helps to avoid material losses.
Aluminium foam is suitable for, amongst other things, vehicle manufacturing, machine structures, the construction industry, railway technology and energy-efficient lightweight construction systems.
Further work is to focus on stable material properties despite fluctuating scrap quality and on comprehensive life-cycle analyses.
