Effect of pre-existing nuclei on microstructure and magnetic properties of high Bs FINEMET-like nanocrystalline alloys

Abstract

The effect of conventional annealing and rapid annealing on the magnetic properties and microstructure of Fe78+2xSi7.2-xB13-xCu0.8Nb1 (x = 0, 1, 2) alloys is discussed systematically. The study was found that the existence of a large number of pre-existing nuclei in the amorphous phase of Fe82Si5.2B11Cu0.8Nb1 alloy can produce tiny nanocrystals and thus result in excellent soft magnetic properties. When the average nanocrystal size is 16 nm using rapid annealing, the best soft magnetic performance can be obtained, in which Bs reaches 1.80 T, Hc is 5 A/m, and μ is 20,000 at 1 kHz. The crystallization kinetics shows that as the Fe content increases, the incubation time of nucleation of the alloys decreases, and the nucleation is faster and easier. In addition, a large number of pre-existing crystal nuclei not only greatly reduces the nucleation activation energy of the alloy but also achieves grain refinement and excellent magnetic properties through grain competition growth.