Pacific Northwest National Laboratory research shows how aluminum waste can be upcycled into high-value aluminum products in a single step.
There’s a well-worn adage in subtractive manufacturing:
“If you’re not making chips, you’re not making money.”
One of the reasons it’s so well-worn is that it cuts to the core of what machining is all about—carving away the useless waste material from metal billets to leave only the high-value components hidden inside. Michelangelo would approve.
But what if that useless waste material could be repurposed? Could the chips themselves make money?
New research from Pacific Northwest National Laboratory (PNNL) suggests the answer to both questions could be “Yes” and that additive manufacturing (AM) could be a key enabler. According to a recent PNNL study, scrap aluminum from industrial waste streams can be upcycled into high-performance metal alloys that perform on-par with identical materials produced from primary aluminum.
The key is a new method called solid phase alloying, which transforms the scrap into usable alloys in a single step. “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, in a press release. “We do this in just a single step, where everything is alloyed in five minutes or less.”
The process converts aluminum scrap blended with copper, zinc and magnesium into a high-strength aluminum alloy in minutes, compared to days required for conventional melting, casting and extrusion. While the research team used a PNNL-patented technique called Shear Assisted Processing and Extrusion, or ShAPE, they claim that their findings should be reproducible with other solid phase manufacturing processes.
The ShAPE process involves using a high-speed rotating die to create friction and heat, which disperses the chunky starting ingredients into a uniform alloy with the same characteristics as a newly manufactured aluminum wrought product. Moreover, the researchers found that, compared to conventional recycled aluminum, the upcycled alloy is 200 percent stronger and has increased ultimate tensile strength, due to the formation of Guinier-Preston zones within the alloy during the ShAPE process.
“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 in the same press release. Powell is 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.”
The solid phase alloying process could be used to create custom metal wire alloys for various 3D printing technologies, Li said. For example, citing wire arc additive manufacturing (WAAM) as an example.
“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.”
The research is published in Nature Communications.
