PNNL and Magna Demonstrate Feasibility of Using ShAPE with Secondary Aluminum for Auto Components

Source: greencarcongress.com

The Department of Energy’s Pacific Northwest National Laboratory has been developing the Shear Assisted Processing and Extrusion (ShAPE) process to enable more cost- and energy-efficient production of high-strength structures from metals and metal alloys for a number of years, with application to a range of different metals. (See the press release.)

Now, in collaboration with Magna, PNNL has demonstrated the feasibility of using ShAPE to manufacture multicell extrusions from secondary aluminum. In a technical report published earlier this year, PNNL and Magna engineers noted that:

"Automotive components made from 100% secondary aluminum offer >50% energy savings and >90% CO₂ savings during the manufacturing process compared to conventional extrusion. Use of secondary Al as the feedstock is not only environmentally friendly but can significantly reduce the cost of components. This is because the need to dilute Fe with primary Al can be eliminated thus removing the energy, carbon, and cost associated with production of primary aluminum. Additionally, lightweight automotive components made from Al alloys offer 25% weight savings compared to state-of-the-art high-strength steel. As a result, steel components are being targeted for replacement by Al where feasible.

"To improve recyclability, this Cooperative Research and Development Agreement (CRADA) between the Pacific Northwest National Laboratory (PNNL) and Magna Services of America (Magna) aimed at developing ShAPE to demonstrate the potential for converting Al industrial scrap directly into sub-scale automotive components.

"Al electric vehicle (EV) battery structures provide one possible insertion opportunity based on equal, or improved performance, at a reduced cost as compared to conventional extrusions. The potential cost reduction and environmental benefits of using feedstock comprised of 100% secondary Al are well established. Use of secondary scrap without the addition of primary Al, however, has not developed into an industry process due to fundamental material challenges associated with intermetallic dispersion and uniform microstructure. These process limitations have been overcome using severe plastic deformation (SPD) techniques, such as equal channel angular pressing (ECAP). Although successful from a scientific standpoint, ECAP and other SPD processes are not scalable to an industrial level. ShAPE combines the microstructural advantages of SPD, with the scalability of a conventional extrusion process to offer a unique technology for converting Al secondary scrap directly into automotive components while meeting industry standard property requirements." —"Shear Assisted Processing and Extrusion (ShAPE) of Lightweight Automotive Components (CRADA 418)"

PNNL’s ShAPE process uses a machine to spin billets or chunks of bulk metal alloy, creating just enough heat through friction to soften the material so it can be easily extruded through a die to form tubes, rods, and channels. The extent of heat generation and depth of the deformation zone is controlled by regulating rotational speed, temperature, and ram speed.

The simultaneous linear and rotational forces use only 10% of the force typically needed to push the material through the die in conventional processes.

This significant reduction in force enables substantially smaller production machinery, thus lowering capital expenditures and operations costs. Energy consumption is similarly low. The amount of electricity used to make a 1-foot length of 2-inch diameter tubing is about the same as it takes to run a residential kitchen oven for just 60 seconds.

To adapt ShAPE for use with secondary aluminum, the engineers integrated a porthole die configuration within the rotating ShAPE process. In a paper published in Manufacturing Letters, the team reports extruding circular, square, trapezoidal, and two-cell trapezoidal profiles from aluminum alloy 6063 industrial scrap.

Microstructural characterization was presented for a trapezoidal profile having an average grain size of 6.7 µm in the as-extruded condition. Round tubes achieved yield strength (246.9 ± 10.4 MPa), ultimate tensile strength (270.8 ± 9.6 MPa), and uniform elongation (16.5 ± 2.4%) exceeding industry standards.

"We showed that aluminum parts formed with the ShAPE process meet automotive industry standards for strength and energy absorption. 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." —Scott Whalen, a PNNL materials scientist and lead researcher

The technical report and research publications mark the culmination of a four-year partnership with Magna, the largest manufacturer of auto parts in North America. Magna received funding for the collaborative research from DOE’s Vehicle Technologies Office, Lightweight Materials Consortium (LightMAT) Program.

The results showed that the ShAPE products are uniformly strong and lack manufacturing defects that could cause parts failure. In particular, the products had no signs of the large clusters of metal—impurities that can cause material deterioration and that have hampered efforts to use secondary recycled aluminum to make new products.

The research team is now examining even higher strength aluminum alloys typically used in battery enclosures for electric vehicles.

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

In addition to Whalen, the PNNL research team included Nicole Overman, Brandon Scott Taysom, Md. Reza-E-Rabby, Mark Bowden and Timothy Skszek. In addition to DiCiano, Magna contributors included Vanni Garbin, Michael Miranda, Thomas Richter, Cangji Shi and Jay Mellis. This work was supported by DOE’s Vehicle Technologies Office, LightMAT Program.

The patented ShAPE technology is available for licensing for other applications.