FeSiBPCu Nanocrystalline Soft Magnetic Alloys with High <I>B</I><SUB>s</SUB> of 1.9 Tesla Produced by Crystallizing Hetero-Amorphous Phase

TLDR

Nanocrystalline soft magnetic alloys typically incorporate elements such as Nb, Zr, Mo, or Cu to achieve nanostructure, but this often reduces saturation flux density and raises material costs. The study aims to develop FeSiBPCu nanocrystalline soft magnetic alloys that overcome the drawbacks of conventional compositions. The authors melt‑spun Fe83.3–84.3Si4B8P3–4Cu0.7 alloys, whose P and Cu additions produce α‑Fe clusters that, upon crystallization, transform into a homogeneous nanocrystalline structure of ~10‑nm α‑Fe grains. The resulting nanocrystalline alloys achieve saturation flux densities of 1.88–1.94 T with coercivities of 7–10 A/m, comparable to commercial Fe‑3.5 %Si alloys, while offering lower material cost and higher productivity.

Abstract

Technically important nanocrystalline soft magnetic alloys and their derivatives always include metal elements such as Nb, Zr, Mo, etc. and/or Cu to realize the nanostructure, which results in a remarkable decrease of saturation magnetic flux density (Bs) and a significant increase in material cost. With the aim to solve the serious problem, we successfully developed new FeSiBPCu nanocrystalline soft magnetic alloys. The melt-spun Fe83.3–84.3Si4B8P3–4Cu0.7 (at%) alloys have heterogeneous amorphous structures including a large amount of α-Fe clusters, 2–3 nm in size, due to the unusual effect of the simultaneous addition of the proper amounts of P and Cu. The hetero-amorphous alloys exhibit higher Bs of about 1.67 T than the representative amorphous and the nanocrystalline alloys, and the low coercivity (Hc) of 5–10 Am−1. A homogeneous nanocrystalline structure composed of small α-Fe grains with a size of about 10 nm can be realized by crystallizing the hetero-amorphous alloys. The nanocrystalline alloys show extremely high Bs of 1.88–1.94 T almost comparable to the commercial Fe-3.5 mass%Si crystalline soft magnetic alloys, and low Hc of 7–10 Am−1 due to the simultaneous realization of the homogeneous nanocrystalline structure and small magnetostriction of 2–3×10−6. In addition, the alloys have a large economical advantage of lower material cost and better productivity than the ordinary soft magnetic nanocrystalline alloys now in practical use.