Addressing the challenge of heavy rare earth supply risk

Permanent magnets (PM) are critical components for electric motors and power generators. The outstanding performances of Nd-Fe-B permanent magnets come from the extrinsic magnetic properties linked to their microstructure. Nevertheless, electrical machines operate at about 120-180°C and magnetic properties decrease rapidly with temperature. To compensate the decrease in magnets coercivity with temperature, it is commonly used to substitute a fraction of Nd with heavy rare earth elements (HRE) such as Dy. However, the supply risk of rare earth elements such as Dy and Nd is high since China has a quasi-monopolistic position in the extraction of HRE.

Another well-established route to increase the coercivity without adding HRE is to reduce grain size in permanent magnet. On the other hand, as the grain size is downsizing below 3µm, the fabrication of magnets with a homogeneous microstructure and effective decoupling of the magnetic grains becomes a significant challenge. Until now, this has not yet been achieved on industrial scale. One limitation of the current production technology is the lack of strip-casted ribbons with optimised microstructure and homogeneity for fine-grained Nd-Fe-B.

Optimised strip-cast process to reduce heavy rare earth content

The goal of UPGRADE is to design and achieve a fine microstructure in the strip-cast ribbons, allowing to reduce the HRE content, that leads to high coercive Nd-Fe-B PM’s. The process to manufacture permanent magnets will be the conventional powder metallurgy route without additional equipment costs.

The value proposition of the optimised strip-cast process is:

  • Reduce the amount of heavy rare earth (HRE) up to 2,5%
  • Improve the magnetic performance
  • Decrease the number of processing steps
  • High health, safety and Environmental standards

First, the microstructure and homogeneity of the ribbons will be optimised for one or several compositions at pilot scale. The outcome will be a NdFeB alloy with refined microstructure at pilot scale. Then, the strip-casting conditions will be leveraged to industrial scale.

Preliminary results from the UpMagnet fast track project in 2017 have clearly demonstrated the potential coercivity increase achievable with fine grained Nd-Fe-B magnets based on optimised ribbons.

Sorana LUCA, Research Engineer – Project Coordinator at CEA

High market potential for new permanent magnet grades

The ambition of the project is to fully exploit the large potential of the strip-cast-process for HRE–lean magnet grades. The achievements will boost development of fine-grained Nd-Fe-B alloys. Additionally, it will allow the extension of the conventional manufacturing processes beyond their current limits. With a growing demand for Electrical Vehicles, requiring a high amount of HRE in high temperature applications, the market potential for the innovative process is high.

The results of the UPGRADE project will have a major beneficial impact on the entire supply chain, from alloy manufacturer to system integration via lower cost, minimised supply risk and reduced impact on the environment.

Sorana LUCA, Research Engineer – Project Coordinator at CEA

The international consortium including research institutes and alloys supplier, a magnet manufacturer and an end-user for assessment represents the complete value chain of the magnet industry:

  • Commissariat à l’énergie atomique et aux énergies alternatives, CEA (French Alternative Energies and Atomic Energy Commission), France (Lead Partner)
  • Centro Ricerche Fiat S.C.p.A. (CRF – C.R.F.), Italy
  • Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. (Fraunhofer), Germany
  • Less Common Metals, United Kingdom
  • Technische Universität Darmstadt, Germany
  • Vacuumschmelze, Germany

The project funded by EIT RawMaterials started in January 2019 for three years.