Allan Walton

Abstract:

In recent years there has been significant price volatility for rare earth magnets based upon neodymium iron boron (NdFeB), which has stemmed from possible supply constraints from the main supplier (China). The Magnetic Materials Group (MMG) has been developing recycling strategies for these materials to mitigate at least some of the supply risk as well as investigating efficient methods of manufacture for fully dense NdFeB magnets. In this presentation Prof Walton will outline the problems encountered when recycling rare earth magnets from end of life products, including identification of magnet type, ease of extraction, problems for purification and complications for re-processing into new materials. He will then propose solutions to these problems including new sensor technologies for identifying magnets in waste, robotic disassembly of magnet containing products and hydrogen based technologies for extraction and reprocessing of sintered magnets.
In the second part of the presentation Prof Walton will outline a new method for producing fully dense NdFeB magnets called the Hydrogen Ductilisation Process (HyDP ref- 1,2,3). During HyDP solid cast NdFeB alloys can be converted into a ductile material at room temperature. This is achieved by converting the cast alloy into a disproportionated structure containing -Fe, NdH2 and Fe2B by processing in hydrogen at between 1-2 bar pressure and > 600^oC. The disproportionated material can be pressed at room temperature and on recombination this produces a small grained anisotropic NdFeB magnetic material. The HyDP process could be used to reduce the yield loss for producing thin magnets compared to conventional sintering processes, it may be possible to process in air which would reduce cost and it could be used to make complex geometries.

1) GB Patent Application -
GB1511553.8. 2015
2) O.Brooks, A.Walton, W. Zhou and I.R.Harris, The Hydrogen Ductilisation Process (HyDP) for shaping NdFeB magnets, Journal of Alloys and Compounds 703 (2017) 538-547
3) O. Brooks, A. Walton, W. Zhou, D. Brown, I.R. Harris, Complete ductility
in NdFeB-type alloys using the Hydrogen Ductilisation Process (HyDP), Acta Materialia (2018), doi:10.1016/j.actamat.2018.04.055.