# Fileset

[REPM2025_P2-33_Schönfeldt.pdf](https://mdr.nims.go.jp/filesets/bb5d91d7-d9ca-49f1-82c9-c8732abd539b/download)

## Creator

Mario Schönfeldt, Jürgen Rossa, Konrad Opelt, Kilian Schäfer, Lukas Schäfer, Fernando Maccari, Matic Jovičević-Klug, Tim M. Schwarz, Chi-Chia Lin, Mahmudul Hasan, Jürgen Gassmann, Dierk Raabe, Oliver Gutfleisch

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[Hydrogen-based functional recycling of Nd-Fe-B sintered magnets from e-mobility and wind power: influence on GBDP microstructure evolution and possibilities to improve the resulting properties](https://mdr.nims.go.jp/datasets/f5c17389-c8a6-4e4b-b16e-0644b733fcc2)

## Fulltext

PowerPoint-PräsentationRecycling of resource-efficient GBDP magnets [1]◼ Hydrogen decrepitation (HD) of over 100 commercial GBDP magnets (0.5 kg)◼ Composition: Nd23.0Pr6.15Tb1.76Dy0.24FebalB0.93Co0.89Ga0.21Al0.13Cu0.08 (wt.%)◼ Jet-milling to particle size D50 of 5.4 μm, aligning, pressing, and sintering at 1100 °C for 4 h followed by annealing at 700 °C for 1 h and 500 °C for 1 h◼ Investigations on the changes of the GBDP microstructure (core-shell) and magnetic properties ◼ GBDP with 1.5 wt.% pure Tb-foil at 900 °C for 9 h with subsequent low-temperature annealing to restore the magnetic propertiesSEM-BSE images, EDS mappings, and EDS line scans through the functionalrecycling process. While at the GBD scrap magnet a narrow Tb-core-shellstructure with 0.5 μm can be observed, the other samples show less clear core-shell formation but broader Tb enrichments at the outer regions of the grains.APT investigation of GBD scrap magnet (left) and recycled magnet (right) revealsbeside a more homogenous distribution of Tb and disappearance of the core-shell microstructure also changes in the grain boundary elemental distributionthrough functional recycling.Hydrogen-based functional recycling ofNd-Fe-B sintered magnets: influence on GBDPmicrostructure evolution and possibilities toimprove the resulting properties—Mario Schönfeldt1,2, Jürgen Rossa1, Konrad Opelt1,2, Kilian Schäfer2, Lukas Schäfer2, Fernando Maccari2, Matic Jovičević-Klug3, Tim M. Schwarz3, Chi-Chia Lin1,2, Mahmudul Hasan1, Jürgen Gassmann1, Dierk Raabe3, Oliver Gutfleisch21 Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS, Aschaffenburger Str. 121, 63457 Hanau, Germany2 TU Darmstadt, Department of Materials and Geosciences, Functional Materials, Peter-Grünberg-Str. 16, 64287 Darmstadt, Germany3 Max-Planck-Institute for Sustainable Materials GmbH, Department of Microstructure Physics and Alloy Design, Max-Planck-Str. 1, 40237 Düsseldorf, Germany[1]  M. Schönfeldt et al., Acta Materialia 283 (2025) 120532.[2] M. Schönfeldt et al., Advanced Engineering Materials, to be published. This work was supported by the Fraunhofer Internal Programs under Grant No. SME 600 004. OGthanks the German Research Foundation (DFG), Project ID No. 405553726, TRR 270 for support andfunding. MJK and TMS thank for the financial support through the Fraunhofer and Max Planckcooperation project MaRS (Critical materials lean Magnets by Recycling and Substitution).A renewed GBDP process at a recycled magnet shows a new formation of Tb-shells, with thickness comparable to the scrap magnet. The coercivity of recycledmagnets can be fully restored. The temperature coefficients exceed the originalvalues which leads to an improved temperature stability of recycled magnets.Classifying of recycled powders [2]◼ High oxidation affinity of fine (< 10 µm) Nd-Fe-B powder particles can lead tocontaminations (e.g., absorption of O2) during recycling◼ Removal of particles < 1 µm should lower the content of impurities◼ HD of 15 kg of EoL-magnets from wind turbines with subsequent milling andclassifying at a spiral jet-millThe classified powder shows a smaller number of finest particles (a). This leadsto a reduction of the oxygen, nitrogen, and carbon content (b), and animproved Br and (BH)max value of the recycled magnets (c).Conclusion◼ GBDP magnets can be recycled with similar rectangular demagnetization curves but reduced coercivity through microstructural changes◼ A renewed GBDP or modified particle size distribution can improve and restore the magnetic properties Fraunhofer IWKSAschaffenburger Str. 12163457 Hanau, Germanywww.iwks.fraunhofer.de