The innovative process could allow the automotive industry to recycle aluminium leftover from car manufacturing processes with 50 per cent less energy and 90 per cent lower emissions than traditional methods.
The new method could remove the need to mine and refine the same amount of raw aluminium ore and also help extend the driving range of electric vehicles (EV). Moreover, by reducing the cost of recycling aluminium, manufacturers may be able to reduce the overall cost of aluminium components, better enabling them to replace steel.
The research has been presented by the Department of Energy of the Pacific Northwest National Laboratory (PNNL), in collaboration with mobility technology company Magna.
"We showed that aluminium parts formed with the 'ShAPE' [Shear-Assisted Processing and Extrusion] process meet automotive industry standards for strength and energy absorption," said Scott Whalen, a PNNL materials scientist and lead researcher. "The key is that the 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."
Aluminium is the second most-used material in the automotive industry after steel. This is due to its light weight and strength characteristics, which allow carmakers to reduce the weight of vehicles and increase fuel efficiency or reduce battery size.
In the process of producing vehicles, carmakers usually rely on the homogenisation of materials, mainly metals. To achieve this, companies pre-heat bricks, or 'billets', to temperatures over 1,000°F (550°C) for many hours. The pre-heating step dissolves clusters of impurities such as silicon, magnesium or iron in the raw metal and distributes them uniformly in the billet.
In contrast, the ShAPE process would allow manufacturers to accomplish the same homogenisation step in less than a second, 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."
The team tested the new process using an aluminium alloy known as 6063, or architectural aluminium, a material used for a variety of automotive components, including engine cradles, bumper assemblies, frame rails and exterior trim.
The PNNL research team examined the extruded shapes using scanning electron microscopy and electron backscatter diffraction, which creates 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 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 aluminium to make new products.
"Sustainability is at the forefront of everything we do at Magna," said Massimo DiCiano, manager of materials science at Magna. "From our manufacturing processes to the materials we use, the ShAPE process is a great proof point of how we're looking to evolve and create new sustainable solutions for our customers."
The research team is now examining even higher-strength aluminium alloys typically used in battery enclosures for electric vehicles.
"This innovation is only the first step toward creating a circular economy for recycled aluminium in manufacturing," said Whalen. "We are now working on including post-consumer waste streams, which could create a whole new market for secondary aluminium scrap."
The team's findings were published in an article in the journal Manufacturing Letters.
