Fe-based Ribbons Research Articles

AFM research on the mechanism of Fe-based alloy stress annealed inducing magnetic anisotropy

The cross-section of the Fe-based alloy (Fe73.5Cu1Nb3Si13.5B9) ribbon annealed at 540°C under various tensile stress was investigated with atomic force microscope (AFM). The stress effect mechanism in Fe-based alloy ribbon tensile stress annealed inducing transverse magnetic anisotropy field was studied using the X-ray diffraction spectra and longitudinal drive giant magneto-impedance effect curves, and the model of direction dominant in encapsulated grain agglomeration was established. The relationship between the direction dominant in encapsulated grain agglomeration and magnetic anisotropy field was disclosed.

Development of Fe-based nanocrystalline materials by mechanical alloying

Two alloys, Fe 80 Nb B 10 and Fe 70 Ni 14 Zr 6 B 10 , were produced by mechanical alloying. The formation of the nanocrystallites (about 7-8 nm at 80h MA) was detected by X-ray diffraction. After milling for 80 h, differential scanning calorimetry scans show low-temperature recovery processes and several crystallization processes related with crystal growth and reordering of crystalline phases. The apparent activation energy values are 315 ± 40 kJ mol –1 for alloy A, and 295 ± 20 kJ mol –1 and 320 ± 25 kJ mol –1 for alloy B. Furthermore, a melt-spun Fe-based ribbon was mechanically alloyed to obtain a powdered-like alloy. The increase of the rotation speed and the ball-to-powder weight ratio reduces the necessary time to obtain the powdered form.

Fabrication of Fe-based ribbon with controlled permeability by Joule heating under tensile stress

We prepared an Fe-based ribbon with controlled permeability and low magnetic loss by continuous stress-annealing by joule heating (CSA-JH) method. The shortest annealing time necessary for the obtaining of the ribbons with completely developed anisotropy was 1 s, but in order to obtain the sufficiently crystallized ribbons with small saturation magnetostriction it is required to perform annealing longer than 2 s. A toroidal core was prepared from a long ribbon with controlled permeability and small saturation magnetostriction, and the magnetic loss and relative permeability of the core were evaluated in the frequency range of 0.1–3 MHz. The permeability was kept constant up to 2 MHz, and the magnetic loss is lower than that for other types of core with a similar permeability value. These results suggest that the CSA-JH method is a promising method for realizing an Fe-based core with excellent magnetic properties.

New fracture morphology of amorphous Fe 78Si 9B 13 alloy

The tensile fracture morphology of a brittle amorphous Fe-based ribbon was investigated by scanning electron microscopy(SEM). The fracture surface consists of mirror, mist and river-pattern zones with crack propagating. The formation of nanoscale damage cavity structure is a main characteristic morphology on the fracture surface. Approaching the fracture source in the mirror, these damage cavities assemble and form the nanoscale periodic striation patterns, which are neither Wallner lines nor crack front waves. At shear deformation stage, the apparent surface energy γ f of amorphous Fe 78Si 9B 13 ribbon is much smaller than that of less-brittle amorphous alloys, which indirectly indicates amorphous Fe 78Si 9B 13 ribbon is perfectly brittle. The crack branching appears at the moment of final fracture due to the high crack propagating velocity.

AFM research on Fe-based nanocrystal crystallization mechanism

The cross-section pattern of Fe-based alloy ribbon (Fe73.5Cu1Nb3Si13.5B9) annealed at different temperatures was investigated by AFM (atomic force microscope), and the effect mechanism of Nb and Cu in Fe-based alloy ribbon annealing was analyzed with XRD diffraction crystal analysis technique and other research results. New concepts of encapsulated grain, Nb vacancy cluster, Nb-B atom cluster and so on were proposed and used to describe the formation mechanism of α-Fe (Si) nanocrystal. Finally, a three-phase (separation phase, encapsulated phase and nanocrystalline phase) interconnected structure model in Fe-based nanocrystalline alloy was established.

Magnetoimpedance effect in surface pinned nanostructured Fe-based alloys

Amorphous Fe-based ribbons of the composition Fe73.5Si13.5B9Nb3Cu1 have been nanocrystallized using conventional heat treatment at 550°C for 60min. Nanostructured ribbons have been irradiated using pulsed Nd:YAG laser (1064nm). To investigate the pinning effect, different energies have been used to illuminate the ribbons. Pinning behavior has been studied using magnetoimpedance data. It has been shown that an increase in laser beam energy makes the pinning centers more effective.

Mesostructure investigation of the transverse magnetic anisotropy field in stress-annealed Fe-based nanocrystalline ribbons

The mesostructure in Fe-based (Fe73.5Cu1Nb3Si13.5B9) nanocrystalline ribbons annealed under different stress (FNRAS) was investigated by observation of the cross section images of the ribbons with atomic force microscopy (AFM) and X-ray diffraction. The longitudinally driven giant magneto-impedance and transversal magnetic anisotropy field (Hk) were measured. The mechanism of the transversal magnetic anisotropy field can be explained by the mesostructure of the directional preference of crystalline grain (coated with amorphous shell) gathering, along the transverse direction, induced in the course of annealing of the Fe-based alloy ribbons under stress.

Magnetic Properties of Fe-Based Ribbons and Toroidal Cores Prepared by Continuous Joule Heating Under Tensile Stress

Nanocrystallized Fe73.5Cu1Nb3Si 15.5B7 ribbons with controlled permeability were prepared by using continuous stress-annealing by Joule heating (CSA-JH) method. An optimization of the annealing conditions revealed that a completely developed anisotropy perpendicular to the ribbon axis can be obtained stably in the moving velocity range from 1 to 200 cm/min at the current density of 37.5 A/mm2. In particular, the highest velocity of 200 cm/min achieved the significant reduction in effective annealing time. The core made from the above-mentioned ribbon had good ac-magnetic properties such as constant permeability up to 2 MHz and low magnetic loss compared with those for different types of cores with controlled permeability. Consequently, it was clarified that the CSA-JH method is one of effective techniques for production of high performance toroidal cores with controlled permeability

Mechanical properties of metallic ribbons investigated by depth sensing indentation technique

The paper presents mechanical properties of two kinds of Co-based and one Fe-based metallic ribbons by the depth sensing indentation (DSI) technique. Investigations were carried out on two kinds ternary alloy Co 77Si 11,5B 11,5 and Fe 78Si 13B 9 and multicomponent Co 68Fe 4Mo 1Si 13,5B 13,5, which are so-called “zero-magnetostriction” materials. Metallic ribbons were investigated in amorphous state and partially crystallized state after annealing in 400°C in argon atmosphere. Heating of ribbons obtained by melt spinning technique was performed to check its effect on changes of mechanical properties.

Fe-based Nanocrystalline Alloy Ribbon as Coaxial Cable Shielding Material

This paper describes the application of an Fe-based nanocrystalline ribbon as a shielding material for coaxial cable in the 10 MHz to 1GHz frequency range. A 0.01 mm thick Fe-based amorphous ribbon was converted into an Fe-based nanocrystalline ribbon by annealing it at 570 °C for 10 min. The ribbon exhibited high impedance characteristics when it was annealed in a transverse magnetic field. The noise attenuation value of cable covered with Fe-based nanocrystalline alloy ribbon annealed in a transverse magnetic field was 12.9 dB. This value exhibited 13 % higher than that of cable covered with Fe-based nanocrystalline alloy ribbon annealed without a magnetic field.

Nanostructure and magnetic properties of As-quenched Fe-based ribbons

Nanocrystalline ribbons Fe-Cu-Nb-Si-B and Fe-Zr-B-Cu with high effective permeability /spl mu//sub e/, high saturation magnetic induction B/sub s/, and low saturation magnetostriction /spl lambda//sub s/ can be fabricated by melt-spinning technique without additional annealing processes. We obtained magnetic properties of B/sub s/=1.23 T, /spl mu//sub e/ (at 1 kHz)=74300,/spl lambda//sub s/=2/spl times/10/sup -6/ for as-quenched nanocrystalline ribbon Fe/sub 72/Cu/sub 2.5/Nb/sub 3/Si/sub 13.5/B/sub 9/, and properties of B/sub s/=1.55 T, /spl mu//sub e/ (at 1 kHz)=27100,/spl lambda//sub s/=-1/spl times/10/sup -6/ for as-quenched nanocrystalline ribbon Fe/sub 87/Zr/sub 7/B/sub 3/Cu/sub 3/, respectively.

A new fabrication process of Fe-based ribbon with creep-induced anisotropy

Continuous stress-annealing process (CSA), in which a ribbon under tensile stress passes through a furnace, was carried out for obtaining long Fe–Cu–Nb–Si–B ribbons with creep-induced anisotropy. It was clarified that the creep-induced anisotropy K uc is almost the same in magnitude for the moving velocity v m range of 1–100 cm/min at the annealing temperature of 530 °C, which suggests that a remarkable reduction in annealing time can be achieved. Furthermore, an increase in annealing temperature enabled us to increase v m up to 275 cm/min. Thus, CSA is an attractive method for applying ribbons with creep-induced anisotropy to mass production.

Application of Fe-Based Nanocrystalline Ribbon to a Noise Filter and a Shielded Cable

The paper describes the application of Fe-based nanocrystalline alloy ribbon to a common-mode noise filter and a shielded cable in the 10 MHz-1 GHz frequency range. A 0.01-mm-thick Fe-based nanocrystalline alloy ribbon exhibited high permeability and high impedance characteristics. The resistance of a 5.5-mm-diameter roll of Fe-nanocrystalline ribbon (12.5 mm wide and 6 cm long) increased from 1.0 /spl Omega/ at 1 MHz to 5.1 /spl Omega/ at 700 MHz. We confirmed that this filter exhibited the same noise attenuation as a conventional filter (ferrite core) but with 1/20th its volume. Moreover, the noise emission from a twisted pair cable is greatly reduced without any increase in the cable volume by employing the nanocrystalline ribbon as a shielding material.

The mechanism of magnetic relaxation in Fe-based nanocrystalline alloy ribbons investigated by permeability spectroscopy

In the present work, in order to elucidate the mechanism of magnetic relaxation in Fe-based nanocrystalline alloy ribbons at low fields and low frequencies, the dependence of the dynamic magnetization properties of nanocrystalline alloy ribbons on the thickness of ribbons has been investigated by permeability spectroscopy. The agreement of the experimental results with the domain wall motion equations confirms that domain wall bulging between the pinning edges is the dominant magnetization mechanism at low fields and low frequencies.

磁性リボン被覆ケーブルのノイズ放射特性

This paper describes the use of an Fe-based nanocrystalline alloy ribbon annealed at 550°C for 10 min as a noise filter. An Fe-based nanocrystalline alloy ribbon wound around an input section of a cable exhibited higher noise attenuation than a conventional magnetic ribbon (Co-based amorphous alloy). Further improvement in noise attenuation was achieved by covering the whole cable with the Fe-based nanocrystalline alloy ribbon. This confirmed that an Fe-based nanocrystalline alloy ribbon is a superior candidate for use as a noise filter and cable shielding material.

The coercivity dependence of giant magneto-impedance effect in Fe–Cu–Nb–Si–B based metallic alloy ribbon at different crystalline stages

We have studied the giant magneto-impedance (GMI) effect in one Fe-based FINEMET alloy ribbon with nominal composition Fe73.5Cu1Nb3Si13.5B9 (at %). DTA experiments were conducted to identify the primary and secondary crystallization temperatures. XRD, SEM and EDAX were performed to identify the phases at various crystalline stages. Static magnetic properties of the ribbons were measured using a VSM. Coercivity was found to be a strong function of annealing temperature, and this, in turn depended on the size and type of the crystalline phases. The maximum MI effect of 103.4% was observed at annealing temperature of 600°C. It was found that a small change in DC coercivity as a result of annealing greatly changed the MI ratios of the crystalline ribbons. Annealing above the secondary crystallization temperature caused the precipitation of Fe2B and Fe3B phases, which induced magnetic hardening and eliminates MI sensitivity.

Nuclear magnetic resonance study of the crystallization kinetics in soft magnetic nanocrystalline materials

We used the nuclear magnetic resonance technique to study the evolution of the structural and magnetic properties of Fe-based melt-spun ribbons of Fe73.5Cu1Nb3Si13.5B9, Fe73.5Cu1Nb3Si18.5B4, and Fe86Zr7Cu1B6, as-cast and annealed at 500, 540, and 430 °C, respectively. Experiments were carried out at 4.2 K and zero-applied magnetic field, and in a controlled radio-frequency (rf) field. This type of measurement allows us to observe B and Nb sites, and makes it possible to distinguish signals associated with regions of different magnetic hardnesses. The results exhibit a high dependence of the spectra on rf power. For Fe–Si-based alloys, we observe well-defined Nb93 resonance signals from three distinct sites according to the concentration of Fe atoms in their neighborhood. In the Fe73.5Cu1Nb3Si18.5B4 spectra we also observe a peak around 34 MHz, connected to the B11 resonance in different Fe–B compounds, which remains as the rf power decreases, suggesting that the signals come from atoms inside a soft magnetic region. As for the Fe–Zr alloy, we also observe a peak around 36 MHz, identified as the B11 resonance, and a broad line around 62 MHz.

Bulk Fe-Based Metallic Glass with Extremely Soft Ferromagnetic Properties

The authors have investigated the DC and AC magnetic properties of a bulk glassy Fe{sub 65.5}Cr{sub 4}Mo{sub 4}Ga{sub 4}P{sub 12}B{sub 5.5}C{sub 5} alloy. In the annealed state the alloy has coercivity H{sub C} and maximum DC permeability {mu}{sub m} of approximately 0.4 A/m (5 mOe) and 2.8 x 10{sup 5}, comparable to those found in annealed zero-magnetostriction Co-based alloys. The low H{sub C} found in the bulk glassy alloy is attributed to the low ratio of surface-roughness to sample thickness, and low residual internal-stress. The total power loss in the annealed bulk glass is about one order of magnitude lower than that of rapidly quenched Fe-based glassy ribbons. This is attributed to a low anomalous eddy-current loss.

Bulk Fe-Based Metallic Glass with Extremely Soft Ferromagnetic Properties

The authors have investigated the DC and AC magnetic properties of a bulk glassy Fe{sub 65.5}Cr{sub 4}Mo{sub 4}Ga{sub 4}P{sub 12}B{sub 5.5}C{sub 5} alloy. In the annealed state the alloy has coercivity H{sub C} and maximum DC permeability {mu}{sub m} of approximately 0.4 A/m (5 mOe) and 2.8 x 10{sup 5}, comparable to those found in annealed zero-magnetostriction Co-based alloys. The low H{sub C} found in the bulk glassy alloy is attributed to the low ratio of surface-roughness to sample thickness, and low residual internal-stress. The total power loss in the annealed bulk glass is about one order of magnitude lower than that of rapidly quenched Fe-based glassy ribbons. This is attributed to a low anomalous eddy-current loss.

The sensitive magnetoimpedance effect in Fe-based soft ferromagnetic ribbons

A comprehensive analysis of magnetoimpedance (MI) phenomena in Fe-based nanocrystalline ribbons is presented in this paper. Giant MI responses have been observed in nanocrystalline samples annealed over the temperature range 490 and . More than 400% increases of the MI ratio were obtained both in and in ribbons. The sensitivity can reach a value larger than in the field range 3 - 7.2 Oe at 800 kHz for ribbons. No MI effect was observed in an as-quenched amorphous sample, because of its very low permeability. A mostly resistive feature was found in an as-quenched amorphous sample. The field dependences of the effective permeability show a typical transverse anisotropy property, and the development of the transverse anisotropy in naturally annealed Fe-based ribbons was analysed.