Yoshihito Yoshizawa

New Fe‐based soft magnetic alloys composed of ultrafine grain structure

Etude des relations entre proprietes magnetiques et compositions, conditions de recuit et microstructure des alliages Fe−Cu−Nb−Si−B

Effects of magnetic field annealing on magnetic properties in ultrafine crystalline Fe-Cu-Nb-Si-B alloys

The relation between magnetic field annealing and magnetic properties in Fe-based alloys called FINEMET, composed of an ultrafine grain structure, have been studied. High-remanence-ratio B-H curves and flat B-H curves can be obtained by longitudinal-field and transverse-field annealing, respectively. The values of core loss and relative permeability of FINEMET alloys annealed in a magnetic field are similar to those of Co-based alloys, and they show excellent soft magnetic properties in the high-frequency range. The alloys annealed in longitudinal fields are suitable for saturable reactors and high-frequency transformers, and those annealed in transverse fields are suitable for choke coils. >

Magnetic properties of FeCuMSiB (M = Cr, V, Mo, Nb, Ta, W) alloys

Abstract Magnetic properties, microstructures and formed phases of nanocrystalline alloys prepared by annealing iron-based amorphous alloys added Cu and M (Cr, V, Mo, Nb, Ta, W) were investigated. Nb, No, Ta, W addition is very effective to improve soft magnetic properties. Especially, Nb is the most effective element to improve the soft magnetic properties. The order of the effect of decreasing the grain size is: Nb = Ta > Mo = W > V > Cr and is similar to that of the sofr magnetic properties.

Common mode choke cores using the new Fe‐based alloys composed of ultrafine grain structure

Common mode choke cores using the new Fe‐based alloys called ‘‘FINEMET’’ composed of ultrafine grain structure were developed. These new cores show high attenuation to high‐voltage pulse noises and good attenuation characteristics over a wide frequency range. Accordingly, the new cores are expected to be applied in many applications as line filters for electronic devices.

Magnetic properties of nanocrystalline FeMCuNbSiB alloys (M: Co, Ni)

Abstract The magnetic properties and microstructure of nanocrystalline FeMCuNbSiB alloys (M: Co, Ni) annealed under a transverse field have been studied. Large induced magnetic anisotropy and good properties in the high frequency range were obtained in Co-rich nanocrystalline FeCo(Cu)NbSiB alloys.

Small-angle neutron scattering and differential scanning calorimetry studies on the copper clustering stage of Fe–Si–B–Nb–Cu nanocrystalline alloys

Abstract The kinetics of copper clustering and primary crystallization of FINEMET type alloys with the compositions Fe 74.5− x Si 13.5 B 9 Nb 3 Cu x and Fe 77 Si 11 B 9 Nb 3− x Cu x have been studied by small-angle neutron scattering (SANS) and high-sensitivity differential scanning calorimetry (DSC) in order to explain the different optimized Cu contents, x , for obtaining the highest permeability in these two alloys. SANS results have shown that the alloys with the optimized Cu contents have the finest nanocrystalline microstructures. Kinetic analyses of Cu clustering prior to primary crystallization have shown that the number density of Cu clusters becomes highest at the crystallization stage of α-Fe primary crystals in the alloy containing an optimized amount of Cu.

Magnetic properties of nanocrystalline Fe82.65Cu1.35SixB16−x alloys (x=0–7)

The Si content dependences of the magnetic properties of the Fe82.65Cu1.35SixB16−x alloys prepared by melt spinning were studied. The maximum Bs and minimum Hc were observed at around x=2 for the annealed Fe82.65Cu1.35SixB16−x alloys. The Bs and Hc of the annealed Fe82.65Cu1.35Si2B14 alloy were 1.84T and 6.5A∕m, respectively. The average grain size of the bcc Fe nanocrystal in the annealed alloys with x⩽2 was about 20nm, it increased with x at x>2. The annealing temperature range without the precipitation of o-Fe3B expanded with Si content.

New High-Bs Fe-Based Nanocrystalline Soft Magnetic Alloys

The magnetic properties and microstructures of newly developed Fe–Cu–B and Fe–Cu–Si–B alloys produced by melt-spinning have been studied. The annealed alloys consist of nanoscale grains. The annealed alloys show a high-saturation magnetic flux density Bs of more than 1.8 T and excellent soft magnetic properties such as a low core loss of about 0.3 W/kg at 50 Hz and 1.5 T (P15/50). For the present alloys, the addition of Cu is effective for the formation of nanoscale grains and the improvement of the soft magnetic properties.

Optimization of the microstructure and properties of Co-substituted Fe–Si–B–Nb–Cu nanocrystalline soft magnetic alloys

The effect of Co replacement for Fe on the microstructure and soft magnetic properties of Fe78.8−xCoxNb2.6Si9B9Cu0.6 (x=5–60) nanocrystalline alloys has been studied for improving the soft magnetic properties of Fe–Si–B–Nb–Cu type alloys at a high frequency range. The magnetic anisotropy constant increases with x, but the coercivity increases when x exceeds 20, indicating that magnetic softness is degraded by replacing Fe with Co. Three-dimensional atom-probe observations have revealed that the number density of Cu-enriched clusters decreases with x, thereby decreasing the number density of the heterogeneous nucleation sites for bcc-Fe primary crystals. In addition, differential scanning calorimetry measurements show that the Cu clustering temperature shifts to a higher temperature with increasing x, suggesting that the kinetics for the Cu clustering decreases as Co content. These experimental results are discussed from the thermodynamical point of view, and the optimized Cu composition to achieve a low c...

Cu addition effect on soft magnetic properties in Fe–Si–B alloy system

The Cu content dependence of the magnetic properties in Fe84−xCuxSi2B14 and Fe82−xCuySi4B14 alloys prepared by melt spinning has been investigated. In the alloy with x=1.35, Bs increases and Hc decreases with annealing temperature TA up to 410°C, while in the alloys with x⩽1.0, Hc markedly increases at around TA=360°C. The values of Bs and Hc obtained in the annealed alloys are Bs⩽1.80T and Hc<7A∕m. With increasing Si content, the optimum Cu content for the appearance of excellent soft magnetic properties becomes higher and the optimum annealing temperature range expands.