National lab reshapes recycled aluminum

In a renewable technology breakthrough, the Department of Energy's Pacific Northwest National Laboratory, in collaboration with leading mobility technology company Magna, has unveiled a process that reshapes aluminum from automotive scrap and trimmings into material for new vehicle parts.

This new manufacturing process, dubbed Shear Assisted Processing and Extrusion (ShAPE), reportedly reduces more than 50% of the energy consumed while simultaneously reducing more than 90% of the carbon dioxide emitted by eliminating the need to mine and refine the same amount of raw aluminum.

Collecting scrap bits and leftover aluminum trimmings from automotive manufacturing, ShAPE transforms it directly into suitable material for new vehicle components – ideally for electric vehicles that benefit from the lightweight metal.

This most recent advancement, described in detail in a new report and in a "Manufacturing Letters" research article, purportedly eliminates the need to add newly mined aluminum to the material before using it for new parts.

By reducing the cost of recycling aluminum, manufacturers may be able to reduce the overall cost of aluminum components, better enabling them to replace steel.

"We showed that aluminum parts formed with the ShAPE process meet automotive industry standards for strength and energy absorption," said Scott Whalen, a PNNL materials scientist and lead researcher. "The key is that ShAPE process breaks up metal impurities in the scrap without requiring an energy-intensive heat treatment step. This alone saves considerable time and introduces new efficiencies."

The recent report and research publication also mark the culmination of a four-year partnership with Magna, the largest manufacturer of OEM auto parts in North America. Receiving funding for the collaborative research from DOE's Vehicle Technologies Office, Lightweight Materials Consortium program, Magna stresses the importance of sustainability as one of its highest values.

"Sustainability is at the forefront of everything we do at Magna," said Massimo DiCiano, Manager Materials Science at Magna. "From our manufacturing processes to the materials we use, and the ShAPE process is a great proof point of how we're looking to evolve and create new sustainable solutions for our customers."

Ideal aluminum

Aluminum is second only to steel when it comes to the materials used by the automotive sector. The advantageous properties of this lightweight metal make it an attractive vehicle material.

Strong and lightweight, aluminum is a key material in a strategy to make lightweight vehicles for improved efficiency, be it extending the range of an EV or reducing the battery capacity size. While the car industry currently does recycle most of its aluminum, it routinely adds newly mined primary aluminum to it before reusing it to dilute impurities.

Metals manufacturers have been relying on a century-old process of pre-heating bricks, or "billets" as they are commonly referred to in the industry, to temperatures of over 1,000 degrees Fahrenheit (550 degrees Celsius) for many hours.

This pre-heating step dissolves clusters of impurities such as silicon, magnesium or iron in the raw metal and distributes them uniformly in the billet through the process known as homogenization.

By contrast, the ShAPE process accomplishes the same homogenization step in less than a second.

Afterward, it transforms the solid aluminum into a finished product in a matter of minutes, with no pre-heating step required.

"With our partners at Magna, we have reached a critical milestone in the evolution of the ShAPE process," said Whalen. "We have shown its versatility by creating square, trapezoidal and multi-cell parts that all meet quality benchmarks for strength and ductility."

For these experiments, the research team selected to work with aluminum alloy 6063, otherwise known as architectural aluminum. This alloy is already used in a variety of automotive components, such as engine cradles, bumper assemblies, frame rails, and exterior trim.

With a target in mind, the PNNL research team examined the extruded shapes using scanning electron microscopy and electron backscatter diffraction, which created an image of the placement and microstructure of each metal particle within the finished product.

The results showed that the ShAPE products are uniformly strong and lack manufacturing defects that could cause parts failure.

In particular, the final pieces had no signs of large clusters of metal – impurities that can cause material deterioration and that have hampered efforts to use secondary recycled aluminum to make new products.

With definitive proof of its effectiveness, the research team is now examining even higher-strength aluminum alloys, those typically used in battery enclosures for electric vehicles.

"This innovation is only the first step toward creating a circular economy for recycling aluminum in manufacturing," added Whalen. "We are now working on including post-consumer waste streams, which could create a whole new market for secondary aluminum scrap."