Optimization of crystallization behavior and soft magnetic properties of the Si-free Fe-B-P-C-Cu nanocrystalline alloys by Cu content tuning

摘要

The effect of Cu content on amorphous forming ability (AFA), crystallization behavior and soft magnetic properties of the new Si-free Fe_(84-x)B_9P_3C_4Cu_x(x = 0.7, 0.9, 1.1, 1.3 and 1.5) alloys were systematically investigated. The phase structure identified by XRD reveals that the alloys for Cu content less than 1.3 at. % have good AFA. The dependence of activation energies of nucleation and growth on Cu content shows that the growth of a-Fe grains is more difficult than the nucleation for the alloy ribbons with Cu ≤ 1.1 at. %, which is beneficial to obtain finer nanocrystalline a-Fe grains during crystallization annealing, while for those with Cu ＞ 1.1 at. %, the growth of a-Fe grains is easier than the nucleation. The relationship between coercivity (H_c) and the annealing temperature (T_a) indicates that appropriate Cu content is beneficial to improve the stability of soft magnetic properties, especially, when annealed near the temperature of the first crystallization peak. The nanocrystalline Fe_(82.9)B_9P_3C_4Cu_(1.1) alloy exhibits a high saturation magnetic flux density of 1.84 T ～ 1.85 T and a low H_c of 13.0 A/m ～ 8.9 A/m annealed in the range of 703 K - 763 K.