Soft magnetic properties of rapidly-annealed nanocrystalline Fe-Nb-B-(Cu) alloys

R. Parsons, B. Zang, K. Onodera, Hidefumi Kishimoto, Takahiro A Kato, K. Suzuki

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Nanocrystalline Fe-M-B (M = Zr or Nb) alloys (Nanoperm) exhibit excellent soft magnetic properties when M content is 6–7 at%. Lowering the M content below 4 at% usually results in a coarsening of the nanocrystallites and so sets a lower limit on the M content for Nanoperm. In this report we have demonstrated that a highly refined, magnetically soft nanostructure can be achieved for Fe-Nb-B-(Cu) alloys with a Nb content well below 4 at% by employing a rapid annealing process which utilises a heating rate of 150 K s−1. The low Nb-content of these nanocrystalline alloys brings about a high saturation magnetic polarization of 1.85–1.9 T, well above the upper limit of Nanoperm (1.7 T). These newly developed, bcc-Fe based nanocrystalline soft magnetic alloys which have an M content lower than 4 at% are named HiB-Nanoperm. HiB-Nanoperm exhibits excellent soft magnetic properties with a coercivity as low as 2.5 A m−1 and a high initial permeability of ∼104 at 1 kHz. A possible explanation for the rapid annealing induced grain refinement observed for this Fe-M-B system is that the higher annealing temperatures used by this process bring about a lowering of the precursor amorphous phase viscosity which then triggers homogeneous nucleation, thereby considerably increasing the number density of bcc-Fe nucleation sites.

Original languageEnglish
Pages (from-to)408-417
Number of pages10
JournalJournal of Alloys and Compounds
Publication statusPublished - 5 Nov 2017


  • Amorphous alloys
  • Induced anisotropy
  • Nanocrystalline alloys
  • Nanoperm
  • Rapid annealing
  • Soft magnetic materials

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