Anisotropic, single-crystalline SmFe12-based microparticles with high roundness fabricated by jet-milling

I. Dirba, J. Li, H. Sepehri-Amin, T. Ohkubo, T. Schrefl, K. Hono

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

Bulk sintered SmFe11Ti-based magnets with high energy density have not been realized yet despite three decades of research efforts. In order to move a step forward in this direction, in this work we demonstrate a process for producing fine, anisotropic, single-crystalline SmFe11Ti-based particles with high roundness by using jet-milling. Particle size of 2.7 ± 0.6 μm is realized in the case of Sm(Fe0.8Co0.2)10.5Cu0.5Ti composition. XRD results show that the ThMn12 phase is preserved during milling, whereas peaks from the intergranular phases vanish indicating partial removal and amorphization as confirmed by TEM studies. Increased roundness can be achieved by optimizing feeding rate and grinding gas pressure, which is beneficial for local demagnetization field reduction according to micromagnetic simulations. Grain boundary infiltration experiments using low-melting alloys enable liquid-phase sintering at a temperature as low as 500 °C. The resultant bulk samples are anisotropic and show full density, although coercivity remains only 0.32 T. The possible reasons are linked to defects in the microstructure, where formation of slip bands lead to Sm vacancies and can lower the local magnetocrystalline anisotropy and the coercivity. It was found that the volume fraction of the defects can be reduced by low temperature annealing of the jet-milled powders.

Original languageEnglish
Pages (from-to)155-162
Number of pages8
JournalJournal of Alloys and Compounds
Volume804
DOIs
Publication statusPublished - 2019 Oct 5
Externally publishedYes

Keywords

  • Jet-milling
  • Permanent magnets
  • Slip bands
  • SmFeTi
  • ThMn

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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