Dramatic grain refinement and magnetic softening induced by Ni addition in Fe-B based nanocrystalline soft magnetic alloys

The effects of Ni addition on the grain size (D) and coercivity (H-c) were investigated for nanocrystalline (Fe1-xNix)(86)B-14 (x = 0-0.3) alloys prepared by ultra-rapid annealing of melt-spun amorphous precursors. Ni addition resulted in a structural change of the nanocrystallites from bcc to fcc and an exceptionally small D of 4.2 nm was obtained at x = 0.3. H-c was reduced dramatically from 6.8 A/m at x = 0 to as small as 2.6 A/m at x = 0.1. This significant improvement of magnetic softness is well understood by the effect of Ni on the local magnetocrystalline anisotropy. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.