High Saturation Magnetization and Soft Magnetic Properties of bcc Fe–Zr–B Alloys with Ultrafine Grain Structure

TLDR

The alloy is produced by annealing melt‑spun Fe–Zr–B ribbons at 873–923 K for 3.6 ks, yielding a bcc phase with 15–20 nm grains; annealing above 973 K causes decomposition to α‑Fe and Fe₃Zr, reducing permeability. The resulting bcc Fe–Zr–B alloys exhibit B₈₀ of 1.60–1.70 T at 800 kA/m and μₑ of 13 000–15 000 at 1 kHz, a lattice parameter of 0.2870 nm, and outperform Fe–Si–B amorphous alloys, making them attractive soft‑magnetic materials.

Abstract

A new soft magnetic material exhibiting high magnetizations (B800) of 1.60 to 1.70 T under an applied field of 800 kA/m as well as high effective permeabilities (μe) of 13000 to 15000 at 1 kHz was produced in Fe–Zr–B alloys ranging from 5 to 7 at% Zr and 2 to 6%B. The material consists of a bcc phase produced by annealing the melt-spun Fe–Zr–B amorphous ribbons for 3.6 ks in the range of 873 to 923 K and the grain size is as small as 15 to 20 nm. The lattice parameter of the bcc phase is about 0.2870 nm which is larger than that of pure α-Fe. The crystallization-induced bcc phase is a metastable phase saturated with the solute elements and the annealing at temperatures above 973 K brings about a decomposition of the bcc phase to α-Fe and Fe3Zr, leading to a drastic decrease of μe. The bcc Fe–Zr–B alloys possess B800 and μe much higher than those of Fe–Si–B amorphous alloys and hence are highly attractive as a new soft magnetic material.