Effects of thermal demagnetisation on the magnetic properties and hydrogen decrepitation of Sm2TM17 sintered magnets
Year: 2026
Type: article
Abstract: Hydrogen Decrepitation (HD) is a potential technique for short-loop recycling of Sm 2 TM 17 sintered magnets from end-of-life (EoL) applications. However, Sm 2 TM 17 magnets retain their magnetisation after hydrogen absorption. Therefore, a demagnetisation step is required to reduce powder handling issues. This work studied the effects of thermal demagnetisation on the nanostructure and HD processing of Sm 2 TM 17 sintered magnets. Sm 2 TM 17 magnets of three commercial grades were heated to 600–1000°C in a vacuum atmosphere and then characterised to investigate their nanostructure and magnetic properties at room temperature. As-received and thermally demagnetised samples were HD processed at 2 bar, 100°C for 72 h and then characterised to determine their hydrogen content, unit cell parameters and degassing behaviour. After thermal demagnetisation at 900°C an irreversible reduction of up to 94% of intrinsic coercivity was observed at room temperature. This was due to Cu segregation from the 1:5H phase lessening the magnetocrystalline anisotropy difference at the 2:17R/1:5H interface. Magnets with greater Cu and Zr content were resistant to this effect and retained stronger domain wall pinning behaviour. Direct reuse of EoL magnets after thermal demagnetisation therefore may require further heat treatment to recover coercivity losses. HD processed thermally demagnetised Sm 2 TM 17 magnets generated powders comparable in size and morphology to as-received material and may be a viable feedstock for recycled magnet manufacture. Therefore, despite the diffusion of Cu at the 1:5H cell boundary, the main hydrogen absorbing 2:17R phase was relatively unaffected, and HD processing was not inhibited.
Source: Materialia
Authors: J. Griffiths, O.P. Brooks, V. Kozak, D. Brown, G. Subramanian, H.S. Kitaguchi, W. Xia, A. Lambourne, A. Campbell, R.S. Sheridan
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $2,400
Funders: Rolls-Royce, University of Birmingham
OpenAlex ID: W7134898435