Soft magnetic properties and core losses of the nanocrystalline FeMB(MZr, Hf, Nb) alloys were found to be improved by optimizing the heating rate(α) in the crystallization process and adding small amounts of Co or Ga elements. The bcc grain size of the alloys was decreasing as a increases in the range below 3.3Ks-1, the soft magnetic properties were significantly improved with increasing a; the effective permeability(μe) at 1kHz for the Fe90Nb7B3 alloy at α = 0.008Ks-1 and 3.3 Ks-1 were 2400 and 29000, respectively. The μe and the Hc were improved by adding small amounts of Co or Ga to Fe90Zr7B3 or Fe84Nb7B9 alloys, respectively. The high Bs of 1.64T combined with the high μe of 27000 at 1kHz and the low core loss of 0.12W/kg at 50Hz and 1.4T were obtained for the (Fe0.985Co0.015)90Zr7B3 alloy. The high permeability of 38000 at 1kHz and the low core loss of 51 Wlkg at 100kHz and 0.2T as well as high Bs of 1.5T were obtained for the nanocrystalline Fe83Nb7B9Ga1 alloy.
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