A new study by researchers at the Department of Energy's Pacific Northwest National Laboratory (PNNL) demonstrates that scrap aluminum from industrial waste can be directly transformed into high-performance alloys without conventional melting processes. Published in Nature Communications, the study outlines a method called solid phase alloying, which provides a cost-effective and environmentally sustainable pathway for producing high-quality recycled metal products.
The research reveals that upcycled aluminum performs comparably to alloys made from primary aluminum. This approach could significantly enhance the value of recycled metal while reducing energy consumption. "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," said Xiao Li, PNNL materials scientist and lead author of the study. "We do this in just a single step, where everything is alloyed in five minutes or less."
A faster and cleaner process
The process combines scrap aluminum with elements such as copper, zinc, and magnesium to create high-strength alloys in minutes -- compared to days using traditional methods like melting, casting, and extrusion. To achieve these results, the team employed a patented PNNL technique known as Shear-Assisted Processing and Extrusion (ShAPE). ShAPE uses a high-speed rotating die to generate frictional heat, dispersing materials into a uniform alloy.
This method avoids energy-intensive melting processes, leveraging low-cost scrap feedstock to reduce production costs. According to researchers, the resulting materials are stronger and more durable than conventional recycled aluminum, making them suitable for various applications, including vehicles, construction, and household appliances.
Stronger, longer-lasting alloys
Mechanical testing and advanced imaging showed that the upcycled aluminum exhibited a unique nanostructure at the atomic level, featuring Guinier-Preston zones -- atomic-scale features that enhance metal strength. Compared to conventionally recycled aluminum, the upcycled alloys are 200% stronger and display improved tensile strength. These properties could extend the lifespan and performance of products made with the material.
Broader applications for solid-phase alloying
The researchers see potential for applying the solid-phase manufacturing method to other metals. "Solid phase alloying is not just limited to aluminum alloys and junk feedstocks," said Cindy Powell, chief science and technology officer for energy and environment at PNNL and a co-author of the study. "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've not been able to make before."
One possible application is in 3D printing. The solid-phase process could produce customized metal wire alloys for wire arc additive manufacturing (WAAM), which builds or repairs metal parts by melting wire feedstock. "It's difficult to obtain feed wires with customized compositions for wire-based additive manufacturing," said Li. "Solid phase alloying is a fantastic way to produce tailored alloys with exact compositions."