Aluminum scrap as a starting material for high-performance alloys

Researchers at Pacific Northwest National Laboratory (PNNL) have developed a method to convert aluminum scrap directly into high-performance alloys without relying on conventional smelting processes.

The results, published in Nature Communications, show that this approach can produce aluminum alloys from industrial waste materials that match the properties of primary aluminum. This opens up new possibilities for cost-effective and environmentally friendly manufacturing processes.

“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 actually transform it from a low-cost waste to a high-cost product,” said Xiao Li, a PNNL materials scientist and lead author of the research study. “We do this in just a single step, where everything is alloyed in five minutes or less.”

The process, called Solid Phase Alloying, combines aluminum scrap with precise amounts of copper, zinc and magnesium. Using a patented technology called Shear Assisted Processing and Extrusion (ShAPE), the material is processed into a homogeneous alloy within minutes. The method uses friction and heat to create a uniform structure that is in no way inferior to conventionally melted aluminum. One advantage of this process is the saving of energy and resources, as energy-intensive melting is no longer necessary. The alloys produced have a 200 percent higher tensile strength than conventionally recycled aluminum, which promises longer durability and better performance.

“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,” said Cindy Powell, the chief science and technology officer for energy and environment at PNNL and a coauthor of this 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 totally new alloys that we’ve not been able to make before.”

Another potential lies in adapting the alloy composition for use in wire-based 3D printing, such as wire arc additive manufacturing (WAAM), where customized wires are a challenge.

“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 such as 2 percent copper or 5 percent copper.”

This research could revolutionize the production of alloys for various applications, from the automotive industry to aerospace. The study was supported by the Solid Phase Processing Science Initiative program at PNNL, which involved a multidisciplinary team.