FeSiBPCu Nanocrystalline Soft Magnetic Alloys with High B-s 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 Fe83.3-84.3Si4B8P3-4Cu0.7 (at%) alloys have heterogeneous amorphous structures including a large amount of alpha-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 1.67 T than the representative amorphous and the nanocrystalline alloys, and the low coercivity (H-c) of 5-10 Am-1. A homogeneous nanocrystalline structure composed of small alpha-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 x 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. [doi: 10.2320/matertrans.MER2008306]