Thermal Stability and Soft Magnetic Properties of Fe–Nb–B Amorphous Alloys with High Boron Concentrations

抄録

Ferromagnetic amorphous Fe–Nb–B alloys containing 30 at%B were found to exhibit a large supercooled liquid region with a temperature interval over 50 K before crystallization and the largest ΔT_x(=T_x−T_g) reaches 71 K for Fe₆₂Nb₈B₃₀. The ΔT_x is strongly dependent on B content, while the soft magnetic properties of saturated magnetization (I_s), permeability (μ_e) and saturated magnetostriction (λ_s) are dependent on Nb content. The Fe₆₂Nb₈B₃₀ amorphous alloy exhibits good soft magnetic properties of 0.68 T for I_s, 2.6 A/m for coercive force (H_c), 19300 for μ_e at 1 kHz and 7.7×10⁻⁶ for λ_s. The crystallization takes place through a single exothermic reaction, accompanying the simultaneous precipitation of the three crystalline phases of α-Fe, Fe₂B and FeNb₂B₂. The crystallization mode which requires long-range atomic rearrangements plays a dominant role in achieving the high stability of the supercooled liquid against crystallization.