Formation and Soft Magnetic Properties of Fe-B-Si-Zr Bulk Glassy Alloys with High Saturation Magnetization above 1.5 T

Abstract

A new Fe-based bulk glassy alloy with good soft magnetic properties and high saturation magnetization (I_s) above 1.5 T was formed at the composition of (Fe_0.75B_0.15Si_0.1)₉₉Zr₁. The addition of 1 at%Zr to Fe₇₅B₁₅Si₁₀ caused the appearance of glass transition (T_g) at 815 K, followed by a supercooled liquid region (ΔT_x (= T_x−T_g)) of 52 K, in addition to a decrease of Curie temperature (T_c) from 714 to 688 K and an increase of crystallization temperature (T_x) from 845 to 868 K . The reduced glass transition temperature (T_g⁄T_l) was measured as 0.59. The increase in the supercooled liquid region enabled us to form bulk glassy alloy rods in the diameter range up to 0.75 mm by the copper mold casting method. The T_c, T_g, ΔT_x and crystallization peak behavior for the bulk glassy alloy rods are nearly the same as those for the corresponding ribbon sample. The bulk glassy alloy rods exhibit high I_s of 1.53 T and low coercive force (H_c) of 2.8 A/m which are comparable to commercial Fe-based amorphous alloy ribbons. The good combination of the new Fe-based alloy composition, high glass-forming ability and good soft magnetic properties indicates that the new bulk glassy alloy may be used as a new type of soft magnetic material.