By optimizing magnets, hybrid and electric cars can be made economically competitive, according to a research project currently underway at St. Pölten University of Applied Sciences in Austria.  

Their project is seeking to find the ideal composition and structure of high-performance permanent magnets intended for use in cars, a move which can help conserve raw materials and they say the ideal designs can be identified quickly and without major expense, thanks to numerical simulation methods.

Hybrid and electric cars need high-performance permanent magnets for best performance but the magnetic materials currently in use require a high proportion of rare earths, which are both expensive and in short supply. Hybrid and electric engines will only be able to boost their economic competitiveness if the amount of certain rare earths required is reduced.

Under the leadership of Prof. Thomas Schrefl, this is precisely what the "Green Cars" research project being undertaken by St. Pölten University of Applied Sciences aims to achieve. State-of-the-art computer simulation methods are being applied to examine how the chemical composition and structure of a magnet influences its performance. This information will then be used to identify ways to optimize the magnetic material so that it requires fewer expensive raw materials, yet continues to deliver the best possible performance.

Raw materials – a Heated Issue

Overall, an electric or hybrid drive contains around two kilos of magnetic material. At present, neodymium iron boron magnets form the basis of this. These have considerably less mass than conventional magnets, but deliver the same level of performance. In order to ensure the magnetic properties are retained even at high temperatures – such as those that occur within a car – the rare earth element neodymium is partially replaced by dysprosium, another rare earth element. This increases the coercive force of the magnet or, in other words, its stability against demagnetization.

However, having recently returned to Austria to join St. Pölten University of Applied Sciences, Schrefl explains that this creates a severe problem: "Compared to neodymium, the proportion of dysprosium in the ore is less than 10 percent. However, the high-performance permanent magnets currently used for hybrid and electric cars contain up to 30 percent dysprosium. In the long term, this will prove problematic when it comes to raw materials, particularly if you consider that, in just a few years, all new cars will be fitted with a hybrid or electric drive."

Understanding Magnets

In cooperation with the University of Sheffield (UK), the "Green Cars" project aims to determine how the proportion of dysprosium can be reduced without compromising the thermal stability of the magnets. In this respect, the researchers say the expertise of St. Pölten University of Applied Sciences in the field of computer simulation is a key advantage.

Applied in conjunction with the finite element method, this is helping to reveal the internal workings of a magnet. The computer is used to break down complex structures into individual elements so that they can be evaluated. Schrefl explains, "We reconstruct the magnet on the computer and break the granular structure of the magnet down into finite elements. By breaking down the microstructure into millions of tetrahedrons and prisms, we can recreate the spatial distribution of the metallic phases within the magnet in a computer model.

We can then use the computer to simulate the effect that changes in the proportion of dysprosium have on the coercive force of the magnet." The finite element method has been applied in the automotive industry for decades, carrying out computer-based crash tests, wind tunnel tests and optimizing designs.