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 Fe _83.3-84.3Si₄B₈P_4-3Cu _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-l0Am^-1. A homogeneous nanocrystalline structure composed of small a-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 1.88-1.94T almost comparable to the commercial Fe-3.5 mass%Si crystalline soft magnetic alloys, and low H_c of 7-lOAḿ¹ 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 oroinary son magnetic nanocrystalline alloys now in practical use.