FeSiBPCu Nanocrystalline Soft Magnetic Alloys with High Bs of 1.9 Tesla Produced by Crystallizing Hetero-Amorphous Phase

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 (B s ) 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 Fe 83.3-84.3 Si 4 B 8 P 3-4 Cu 0.7 (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 B s of about 1.67T than the representative amorphous and the nanocrystalline alloys, and the low coercivity (H c ) of 5-10Am -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 B s of 1.88-1.94 T almost comparable to the commercial Fe-3.5 mass%Si crystalline soft magnetic alloys, and low H c of 7-10Am -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.