| By adjusting the technics parameters through annealing process to control the types of nanocrystalline precipitates phases, the size of nano-crystal and the nanocrystalline volume fraction is an important method to obtain excellent soft magnetic properties for nanocrystalline soft magnetic materials. Also, it has been pointed out that magnetic field annealing (TFA) can further optimize soft magnetic properties such as reduce coercivity (Hc) and core loss (W), which can contribute to energy conservation and environmental protection. On the other hand, inductance (Ls) is also an important parameter of nanocrystalline magnetic core for electronic components application. With larger Ls, the nanocrystalline magnetic core is more sensitive and effective impedance to the AC interference signal, which is more beneficial to application in signal screening, noise filtering and current stabilizing. However, there is few report about the influence of magnetic field annealing conditions on magnetic properties of nanocrystalline magnetic core with high inductance. Thus, in this work, we investigated the inductance and magnetic properties variation for Fe73.5 Cu1Nb3Si15.5B7 alloy annealed under no field (NFA) and TFA and the relationship between microstructure and magnetic properties was also investigated.Nanocrystalline magnetic core with ribbon thickness was 20 ?m annealed under 550 ?,60 min exhibits high Ls of 14.7 ?H and high Hc of 2.0 A/m. Based on the research results, transverse magnetic field annealing (TFA) were carried out on Fe73.5Cu1Nb3Si15.5B7 nanocrystalline magnetic core, aiming at decreasing the coercivity (Hc) while keeping the high inductance (Ls). The magnetic field generated by direct current (DC) was applied on the magnetic core during different selected annealing stages and it was proved that the nanocrystalline magnetic core achieved lowest Hc when applying transverse field during the whole annealing process (TFA1). Hc of the nanocrystalline magnetic core annealed under TFA1 decreased along with the increasing magnetic field. As a result, the certain size nanocrystalline magnetic core with low Hc of 0.6 A/m, low core loss (W at 20 kHz) of 1.6 W/kg under flux density of 0.2 T and high Ls of 13.8 ?H measured under 0.3 V and 100 kHz were obtained after TFA1 with the DC intensity of 140 A. The combination of high Ls with excellent magnetic properties promised this nanocrystalline alloy an outstanding economical application in high frequency transformers.Although the microstructure and crystallization degree of the nanocrystalline magnetic core exhibited no obvious difference after TFA1 compared to NFA, the value of mean square deviation (?) for TFA1 sample significantly lower than NFA and gradually decrease with the increasing current. When more uniform nanostructure with a smaller mean square deviation of grain size distribution. What is more, the a is 1.80 for TFA1 (I= 140 A) sample, which is much smaller than that of NFA sample (?NFA= 2.46), reflecting a more uniform grain size distribution. It is suggested that the nucleation activation energy for primary crystal phase is decreased under field annealing, which results in the increase of nucleation rate and density, whereas the crystallization mechanism is not changed. Also, when transverse magnetic field is applied, uniaxial anisotropy Ku, induced with axis parallel to the direction of magnetic field, dominates over other anisotropies and simple transverse slab domains are formed, which largely reduce the Hc and ?m. |
PDF Full Text Request