Formation of Nanocrystalline Structures by Crystallization of Amorphous Fe-M-B (M=IVa to VIa Group Metal) Alloys

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The formation range, crystallization behavior, annealing-induced phase and its magnetic properties were investigated for amorphous Fe_<93-x>M_7B_x (M=Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W) alloys. It was found that the crystallization process of the amorphous Fe-M-B alloys can be classified into two types where the primary precipitates are a bcc single phase (M=Zr, Hf, V, Nb, Cr and Mo) or coexistent bcc and tetragonal-Fe_3B phases (M=Ti, Ta and W). The grain size of the primary crystallized Fe-M-B alloys was evaluated to be 10 to 20 nm for M=Ti, Zr, Hf, Nb, Ta and W, being smaller than those (30 to 50 nm) for M=V, Cr and Mo. The small grain size of the alloys containing the former M elements seems to reflect the small growth rate of the primary precipitates resulting from the large re-distribution of the M elements between the primary bcc and residual amorphous phases which is due to their small solubility to α-Fe as well as their small diffusivity. The volume density of primary bcc precipitates showed the tendency to increase with increasing heating rate. This microstructural change results in a significant increase of the permeability (μ_e) of the nanocrystalline alloys and high μ_e values of 24000-38000 at 1 kHz and 0.4 A/m are obtained for the Fe-M-B (M=Zr, Hf and Nb) alloys annealed with a heating rate of 3.3 K/s.nanocrystalline alloyscrystallizationsoft magnetic propertiesamorphous alloys
東北大学の論文
1994-03-25