Metal scrap can now be transformed into high-performance, high-value alloys without traditional melting processes, according to researchers at the Department of Energy’s Pacific Northwest National Laboratory (PNNL). Their study, published in Nature Communications, highlights a new method called solid-phase alloying that turns scrap aluminum from industrial waste streams into high-performance alloys.
An innovative new solid phase alloying process eliminates the need for the costly and energy-intensive melting, casting and extrusion process currently used for aluminum recycling. Image Credit: Nathan Johnson Pacific Northwest National Laboratory
The upcycled aluminum matches the performance of materials made from primary aluminum, offering a cost-effective pathway for introducing premium recycled metal products to the market. This method not only enhances material properties but also supports environmental sustainability by converting waste into valuable aluminum products.
The novelty of our work here is that by adding a precise amount of metal elements into the mix with aluminum chips as a precursor, you can transform it from a low-cost waste to a high-cost product. We do this in just a single step, where everything is alloyed in five minutes or less.
Xiao Li, Materials Scientist and Study Lead Author, Pacific Northwest National Laboratory
The solid-phase alloying process blends aluminum scrap with copper, zinc, and magnesium to create high-strength alloys in minutes. In contrast, conventional methods involving melting, casting, and extrusion can take days to achieve similar results. The team relied on a PNNL-patented technique called Shear Assisted Processing and Extrusion (ShAPE) to produce these alloys, though the findings could be replicated using other solid-phase manufacturing methods.
Within the ShAPE process, a high-speed rotating die generates heat and friction, dispersing the raw materials into a uniform alloy. The resulting material shares the properties of newly manufactured aluminum but is produced without the need for energy-intensive bulk melting. Combined with low-cost scrap feedstocks, this approach could significantly reduce production costs. For consumers, this means more durable and affordable aluminum products for applications like vehicles, construction materials, and household appliances.
Metal Alloy that is Strong to the Core
The scientific team investigated the internal structure of the recycled materials made by solid phase alloying using both mechanical testing and sophisticated imaging. Their findings demonstrated that the recycled alloy ShAPE imparts a distinct atomic-level nanostructure. Atomic-scale characteristics known as Guinier-Preston zones develop inside the alloy during ShAPE.
It is commonly known that these characteristics increase the strength of metal alloys. The upcycled alloy has a higher ultimate tensile strength and is 200% stronger than traditional recycled aluminum. These qualities may result in products that last longer and perform better for customers.
Our ability to upcycle scrap is exciting, but the thing that excites me the most about this research is that solid phase alloying is not just limited to aluminum alloys and junk feedstocks. Solid phase alloying is theoretically applicable to any metal combination that you can imagine, and the fact that manufacturing occurs wholly in the solid state means you can begin to consider new alloys that we have not been able to make before.
Cindy Powell, Chief Science and Technology Officer, Study Co-Author, Pacific Northwest National Laboratory
The solid-phase alloying process also has potential applications in producing custom metal wire alloys for 3D printing technologies. For example, wire arc additive manufacturing (WAAM) uses a robotic welding torch to melt metal wires and create 3D parts. However, obtaining feed wires with customized compositions for such processes can be challenging.
It is difficult to obtain feed wires with customized compositions for wire-based additive manufacturing. Solid phase alloying is a fantastic way to produce tailored alloys with exact compositions such as 2 % copper or 5 % copper.
Xiao Li, Materials Scientist and Study Lead Author, Pacific Northwest National Laboratory
This recycling technology transforms scrap aluminum into high-strength building materials and more
Learn more about how PNNL’s solid phase processing is transforming scrap aluminum into valuable products. Video Credit: Pacific Northwest National Laboratory
Journal Reference:
Wang, T., et al. (2024) Upcycled high-strength aluminum alloys from scrap through solid-phase alloying. Nature Communications. doi.org/10.1038/s41467-024-53062-2.