We obtained Fe84Nb7B9 bulk alloys by extruding amorphous powders at temperatures (Te) between 653 and 723 K and pressures (Pe) of 820 to 1210 MPa, and Fe90Zr7B3 bulk alloys by extruding at Te of 673 to 698 K and Pe of 920 to 940 MPa. Subsequent annealing of these bulk alloys at 923 K for 3.6 ks causes the formation of a nanocrystalline bcc phase with grain sizes of 9 to 11 nm for Fe84Nb7B9 and 20 to 30 nm for Fe90Zr7B3. The bcc Fe84Nb7B9 bulk alloy exhibits a magnetization (B800) of 1.40 T, a permeability (μe) of 1120 at 300 Hz, and a coercive force (Hc) of 48 A/m in the extrusion condition of Te = 698 K and Pe = 870 MPa. Similarly, the B800, μe and Hc of the bcc Fe90Zr7B3 bulk alloy prepared at Te = 698 K and Pe = 923 MPa are 1.57 T, 1880 and 29 A/m, respectively. The soft-magnetic properties of the bcc Fe90Zr7B3 bulk alloy are superior to those of the bcc Fe84Nb7B9 bulk alloy, presumably because of the formation of a more homogeneous bcc structure for the former alloy.
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