Fe-based Nanocrystalline Soft Magnetic Alloys Research Articles

Novel FePCB nanocrystalline alloys induced by indium microalloying

In this work, novel Fe86-xP11C2B1Inx (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) amorphous alloys were developed. After proper annealing of the amorphous precursor, Fe85.8P11C2B1In0.2 nanocrystalline alloy, with relatively low coercivity (Hc) and high saturation magnetization (Bs) in the range of 2.9–21.0 A/m and 1.63–1.73 T, was obtained. The structure of the nanocrystalline structure was investigated and confirmed by XRD and TEM. The results indicate that In microalloying can induce the nanocrystallization in FePCB amorphous alloy, which was proved by Kissinger’s plot. It provides a new way to develop new Fe-based nanocrystalline soft magnetic alloys.

Critical Influence of Glassy State on Nanocrystallization of Amorphous Precursors in Fe-Based Nanocrystalline Soft Magnetic Alloys

Critical Influence of Glassy State on Nanocrystallization of Amorphous Precursors in Fe-Based Nanocrystalline Soft Magnetic Alloys

Preparation of flake-shaped Fe-based nanocrystalline soft magnetic alloy particles subjected to plastic deformation

ABSTRACT Fe-based nanocrystalline alloy powder prepared by ball-milling is a potential candidate as a soft magnetic composite (SMC). Since the magnetic properties of particles having a random geometry arising from brittle fracture deteriorate by the presence of a demagnetising field, plastically deformed flake-shaped powders, exhibiting better magnetic properties on account of the suppression of any demagnetising field, are desirable. Microstructure such as grain size, lattice distortion and the distribution of dislocations, are affected by ball-milling treatment which changes the magnetic properties. In this study, Fe-based nanocrystalline alloy sheets are ball-milled with lubricant oil as a process control agent (PCA) and the microstructure of the particles investigated. The PCA effectively suppresses the brittle fracture of the alloy sheet during the ball-milling treatment and plastically deformed flake-shaped particles are then successfully obtained. Transmission electron microscopy reveals that there were few lattice defects in the α-Fe grain of the alloy, which indicated that almost only grain-boundary-mediated processes such as GB diffusion/sliding/migration and grain rotation dominate the deformation mechanism. However, Williamson–Hall analysis based on synchrotron radiation exhibits a slope indicating micro-strain in the α-Fe grains. It is found that the plastic deformation induced by the ball-milling treatment forms a microstructure having lattice distortion but containing few lattice defects. It is considered that a slight growth of the existing grains, which can be induced by thermal treatment, can achieve a strain- and dislocation-free microstructure, which is desirable for soft magnetic alloys.

Grain refinement mechanism of soft-magnetic alloys with nanocrystals embedded in amorphous matrix

To obtain uniform and stable nanostructure with fine α-Fe grains is very important for the wide applications of Fe-based nanocrystalline soft-magnetic alloys. In this study, the nanostructure evolution of the Fe84.75Si2B9P3C0.5Cu0.75 (at.%) alloy after annealing under different conditions was characterized in detail. It is found that the alloy exhibits excellent structural stability, which can maintain small α-Fe grains for a prolonged annealing time at low temperature. The increase of annealing temperature and/or annealing time will lead to the precipitation of compound phases in the intergranular amorphous interphase, which affects the α-Fe grains size greatly and determines the structural stability. The elemental mappings of the nanostructured alloys reveal that metalloid elements are enriched in the intergranular amorphous interphase, wrapping around α-Fe grains. The grain refinement and nanostructure stability of these alloys are derived from the shielding and soft-impingement effects of the core-shell like structure. The nanostructure stability is lost with the precipitation of compound phases in the intergranular amorphous interphase, owing to the break-down of the shielding layer, which results in the rapid coarsening of α-Fe grains by coalescence.

High saturation magnetic flux density of Novel nanocrystalline core annealed under magnetic field

In the present study, the magnetic and microstructural properties were investigated of Fe-based nanocrystalline soft magnetic alloy with the composition of Fe80Si7B9Nb3Cu1 fabricated by the melt-spinning method. The annealing under varying transverse magnetic field was applied to induce the uniform distribution of α-Fe nanocrystals. The lowest core loss (Pcv) was 124.0 mW/cm3 achieved with the specimen annealed at 560 °C. Furthermore, the core annealed at 560 °C showed the Bs as high as 1.57 T which is significantly higher than that of conventional FINEMET core (Bs = 1.23 T). The combination of high Bs with excellent magnetic properties makes this nanocrystalline alloy a promising candidate for the application in high frequency (f) region.

Structural and Magnetic Characterization of Fe-Based Amorphous Alloy Prepared by Microwave Annealing Treatment

Fe-based nanocrystalline soft-magnetic alloy presents the advantages of high permeability and low hysteresis loss and is widely used in the power electronics industry due to its excellent soft-magnetic properties. The effects of microwave annealing on the crystallization process and properties of Fe80.5Si10B8Cu1Nb0.5 amorphous alloy have been studied by differential scanning calorimetry, x-ray diffraction analysis, and vibrating-sample magnetometry. The crystallization process of Fe80.5Si10B8Cu1Nb0.5 amorphous alloy consists of two stages: α-Fe(Si) phase and Fe2B phase. The microwave annealing process enables a significant improvement in the soft-magnetic properties of Fe-based amorphous alloy, with the optimum magnetic properties being obtained for the alloys annealed at 1000 W for 10 min.

Nanocrystalline soft magnetic materials from binary alloy precursors with high saturation magnetization

A brief survey of the recent advances in Fe-based nanocrystalline soft magnetic alloys has shown that the saturation magnetization (Js) of these alloys is governed by the mass fraction, rather than the atomic fraction, of the nonmagnetic additives. Thus, the ultimate limit of Js in the alloys prepared by nano-crystallization of amorphous precursors is expected in an Fe-B binary system where amorphization by rapid quenching takes place with the lowest mass fraction of glass forming elements in Fe-based systems. We will demonstrate that nano-crystallization is possible in this binary system when the precursor amorphous phase is annealed ultra-rapidly. While the grain size after conventional annealing for amorphous Fe-B alloys is too large for the exchange softening effect, a small grain size well below the exchange length is obtained after annealing with a heating rate of 103 – 104 K/s. This results in magnetically soft nanostructures with Fe content up to 97.2 wt. %, leading to a high Js ≥ 1.9 T with a small coercivity (Hc) between 3.8 and 6.4 A/m. An addition of Co to nc-Fe87B13 results in a higher Js of 2.0 T with a slight increase of Hc to 9.3 A/m. The soft magnetic properties of these ultra-rapidly annealed alloys (named HiB-Nanoperm) is well understood by the random anisotropy model. The formation of nano-meter scale microstructures in a simple binary system unlocks previously unavailable alloy design strategies in nanostructured systems which is not only relevant to magnetic materials but, also to structural materials.

Enhanced Sensitivity With Five-Phase Heterostructure Magnetoelectric Sensor at Low Magnetic Bias Field

In this paper, we have proposed a five-phase heterostructure magnetoelectric (ME) sensor with high-permeability Fe-based nanocrystalline soft-magnetic alloy FeCuNbSiB, ferromagnetic alloy with constant elasticity FeNi and piezoelectric ceramic lead zirconium titanate (PZT). A built-in magnetic field induced by a spatially varying magnetization within the heterostructure leads to a zero-biased ME response. The corresponding zero-biased ME coefficient reaches as high as 43.75 V/ $\text {cm}\cdot \textrm {Oe}$ (3.5 V/Oe). Meanwhile, an additional stress produced by FeCuNbSiB is transferred to FeNi, which enhances the effective resonant strain coefficient for FeCuNbSiB/FeNi at low magnetic bias and decreases the required optimum dc magnetic bias $H_{\mathrm{opt,dc}}$ . Hence, the maximum resonant ME coefficient is found to reach 51.5 V/ $\text {cm}\cdot \textrm {Oe}$ (4.12 V/Oe) at $H_{\mathrm{opt,dc}}$ of only 33 Oe. $H_{\mathrm{opt,dc}}$ for our proposed ME sensor is about one-tenth of that for FeNi/PZT/FeNi. Correspondingly, the five-phase heterostructure ME sensor is able to possess the strong ME sensitivity at low bias or even zero bias.

Development of FeSiBNbCu Nanocrystalline Soft Magnetic Alloys with High B s and Good Manufacturability

In order to develop Fe-based nanocrystalline soft magnetic alloys with high saturation magnetic flux density (Bs) and good manufacturability, the effect of the Nb content on the thermal stability, microstructural evolution and soft magnetic properties of Fe78−xSi13B8NbxCu1 (x = 0, 1, 2 and 3) alloys were investigated. It is found that proper Nb addition is effective in widening the optimum annealing temperature range and refining the α-Fe grain in addition to enhancing the soft magnetic properties. For the representative Fe76 Si13B8Nb2Cu1 alloy, the effective annealing time can be over 60 min in the optimal temperature range of 500–600°C. FeSiBNbCu nanocrystalline soft magnetic alloys with desirable soft magnetic properties including high Bs of 1.39 T, low coercivity (Hc) of 1.5 A/m and high effective permeability (μe) of 21,500 at 1 kHz have been developed. The enhanced soft magnetic performance and manufacturability of the FeSiBNbCu nanocrystalline alloys are attributed to the high activated energy for the precipitation of α-Fe(Si) and the second phase. These alloys with excellent performance have promising applications in electromagnetic fields like inductors.

Softening and good ductility for nanocrystal-dispersed amorphous Fe–Co–B alloys with high saturation magnetization above 1.7 T

Abstract Fe 80−x Co 20 B x (x = 12–15 at%) alloy ribbons consisting of single bcc phase (12%B), amorphous plus bcc-Fe(Co) mixed phases (13%B) and amorphous single phase (14%B and 15%B) were synthesized by the melt-spinning technique. It is noticed that all the alloy ribbons containing amorphous phase exhibit good bending ductility in the as-spun state and even after annealing which leads to the precipitation of nanoscale bcc-Fe(Co) phase. The amorphous plus bcc-Fe(Co) phase alloys with lower hardness exhibited a number of microcracks in the region near the hardness indentation trace, in addition to distinct slip step markings. The decrease in hardness and the maintenance of ductility in the nanocrystalline state are interpreted to originate from microcrack-induced softening phenomenon. The nanocrystalline alloys also exhibit good soft magnetic properties with high saturation magnetization above 1.7 T in combination with low coercivity of about 20 A/m. The good bending ductility as well as the microcrack-induced softening for the amorphous alloys including nanoscale bcc-Fe(Co) phase is believed to be the first evidence in the long development history of Fe-based nanocrystalline soft magnetic alloys. The finding of the ductile Fe-based nanocrystalline alloys with high saturation magnetization is encouraging for further extension of nanocrystalline magnetic materials.

Self-biased magnetoelectric coupling characteristics of three-phase composite transducers with nanocrystallin soft magnetic alloy

This paper reports the self-biased magnetoelectric (ME) effects in composites consisting of high-permeability Fe-based nanocrystalline soft magnetic alloy Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB), pure nickel (Ni) and piezoelectric lead zirconate titanate (PZT). The FeCuNbSiB ribbons are fabricated on traditional laminates Ni/PZT/Ni through two modes: the attached mode (F–NPN–F) and the laminated mode (F/NPN/F). The F–NPN–F composite sufficiently reveals that the high-permeability FeCuNbSiB ribbons concentrate more magnetic flux in magnetostrictive Ni, which results in the self-biased ME effects of F–NPN–F. For the F/NPN/F composite, the FeCuNbSiB acts as the dynamic driver to enhance the effective piezomagnetic coefficient of Ni. The giant self-biased ME effects of F/NPN/F are because of the internal magnetic field between Ni and FeCuNbSiB due to their different magnetic characteristics. The influences of the numbers of FeCuNbSiB layers (L) on the resonant ME voltage coefficients (α ME,r ) for F–NPN–F and F/NPN/F composites are investigated in detail. The experiments demonstrate that the maximum α ME,r at zero-biased field is 80 V/cm Oe for F–NPN–F with L = 2, and 85 V/cm Oe for F/NPN/F with L = 4. This paper demonstrates that these two ME composites are suitable for achieving zero-biased ME transducers, power-free magnetic field sensors and energy harvesters.

Investigation on comprehensive performance of the EFI by MIM technology

Metal Injection Molding (MIM) technology is introduced into EFI production processing. Magnetic circuit of EFI is designed, and three different kinds of EFI samples are manufactured. Through comparisons of simulation and ex- periments, comprehensive performance of one EFI sample, which is made of Fe-based nanocrystalline soft magnetic alloy by MIM is found to be obviously better than that of others, which are made of traditional material and processing. The dynamic response times of opening and closing are respectively shorter by 32.5% and 62.2%, and dynamic flow range is wider by 8.3%. The electronic fuel injector (EFI) is a key actuator of gasoline engine, which decides precision of fuel injection, so characteristics of EFI, such as accuracy, consistency and stability, are mostly important for engine fuel injecting system. The key parts of injector are traditionally made of soft magnetic alloy bar through metal machining process, technology of which is characterized by low efficiency, material utilization and poor consistency. Moreover, cutting stress, caused while cut- ting, would lead to permeability of soft magnetic materials decreasing, coercivity and magnetic wastage increasing (1). Metal Injection Molding (MIM) known as the most popular parts forming technology, is a new near-net shaping technique (2). MIM technology is a product of multi- disciplinary cross-penetration, such as plastic injection molding polymer chemistry, powder metallurgy technology and metal material science (3). High density, high precision and high strength parts can be manufactured rapidly by MIM technology. MIM can be traced back to 1920's, when ceramic spark plug was prepared with process of powder injection molding. Several decades from then, powder injection molding was mainly applied to ceramic injection molding. Until 1979, Par- match Co., establishedby Wiech, turned its application from powderinjection molding into metal injection molding for first time (4). Through almost twenty years of development, MIM technol- ogy is widely used in aerospace, weapon, car, tools, teeth materials, medical materials, national defense and people's livelihood industry (5-12), for its advantages of high productivity, high precision and high performance.

Investigation of magnetostrictive/piezoelectric multilayer composite with a giant zero-biased magnetoelectric effect

In this paper, we investigate the resonance magnetoelectric (ME) effect in the middle supported multilayer composites consisting of high-permeability Fe-based nanocrystalline soft magnetic alloy Fe73.5Cu1Nb3Si13.5B9 (FeCuNbSiB), Nickel (Ni), and piezoelectric Pb(Zr1−x Ti x )O3 (PZT). The coupling effect between positive magnetostrictive FeCuNbSiB and negative magnetostrictive Ni results in the build-in magnetic bias due to their different magnetic permeability and coercivity. As a result, a giant resonance ME voltage coefficient (α ME,r ) at zero DC magnetic bias field (H dc) and multi-peaks of α ME,r for FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB composite are observed. The experimental results show that the giant zero-biased α ME,r strongly depends on the thickness of FeCuNbSiB ribbon. The maximum zero-biased α ME,r is up to 86 V/cm Oe for FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB with four-layer FeCuNbSiB ribbons, which is ∼500 times higher than that of the previously reported NKNLS-NZF/Ni/NKNLS-NZF trilayer composite. Compared with the peak α ME,r and the optimum H dc of Ni/PZT/Ni composite, the largest peak α ME,r of FeCuNbSiB/Ni/PZT/Ni/FeCuNbSiB composite with four-layer FeCuNbSiB ribbons increases ∼185 %, and the optimum H dc decreases ∼300 Oe, respectively. Based on the nonlinear magnetostrictive constitutive relation and the magnetoelectric equivalent circuit, a theoretical model of α ME,r versus H dc is built under free boundary conditions. Calculated zero-biased α ME,r and α ME,r versus H dc are in good agreement with the experimental data. This laminate composite shows promising applications for high-sensitivity power-free magnetic field sensors, zero-biased ME transducers and small-size energy harvesters.

Recent progress in high Bs Fe-based nanocrystalline soft magnetic alloys

High saturation magnetic flux density (high-Bs) alloy has been developed in an Fe-based nanocrystalline alloy system. A nanocrystalline phase with an average grain size of about 20 nm is obtained by annealing Cu-substituted and/or Cu-and-Si-complex-substituted Fe–B amorphous alloys. The alloy exhibits low coercivity of less than 7 A m−1 and a high Bs of more than 1.8 T. The iron loss at 50 Hz and 1.6 T for a toroidal core made of Fe80.5Cu1.5Si4B14 nanocrystalline alloy is 0.46 W kg−1, which is about 2/3 of that of grain-oriented Si steel. Moreover, the iron loss at 10 kHz and 0.2 T for a wound core made of this alloy is 7.5 W kg−1, which is about 25% of that of non-grain-oriented Si steel and about 60% of that of an Fe-based amorphous alloy. In addition, the cut cores made of the alloy show good superimposed dc-current characteristics and appear promising in applications such as power choke coils (at the high-frequency region).

Fe-based nanocrystalline soft magnetic alloys for high-temperature applications

We report on improved high-temperature soft magnetic properties in Fe88−2xCoxNixZr7B4Cu1 nanocrystalline alloys. Substituting 5.5 at. % Co and Ni for Fe enhances the magnetization by 5% at ambient temperature and by 30% at 650 °C. The Curie temperature of the residual amorphous phase is also raised significantly (from 67 °C for x=0 to 298 °C for x=5.5), resulting in low coercivities (<30 A m−1) for Fe77Co5.5Ni5.5Zr7B4Cu1 over the temperature range 50–500 °C. The higher magnetization and Curie temperature as compared with other Fe-based alloys, and smaller Co content as compared with (Fe,Co)-based alloys, make this alloy attractive as an affordable high-temperature soft magnetic material.

Magnetic and frequency properties for nanocrystalline Fe–Ni alloys prepared by high-energy milling method

Fe-based nano-crystalline soft magnetic alloy with Ni-doping was fabricated successfully by high-energy milling. It was proved that a Fe–Ni solid solution is formed and the evaluated average grain size is about 20nm. The effect of doping Ni on the frequency properties was systematically investigated. From the magnetic measurement results, it can be concluded that, the nickel doped decreases the resonance frequency of Fe–Ni alloy, but Ni doping enhances the frequency stability. The corresponding value of initial permeability as a function of Ni doping concentration was given at 10kHz and the result indicates that the peak value of initial permeability shifts to the region of low Ni concentration for the samples milled for 72h.

UV pre-ionized wide-aperture XeCl laser using magnetic pulse compression

To provide a spatially homogeneous and sufficiently high-voltage discharge, the laser described here used LC inversion and two-stage magnetic pulse compression in the excitation circuit and used UV radiation for pre-ionization. It also employed one commercial thyratron as a high-voltage switch. Evaluation of the dynamic magnetic characteristics of four magnetic materials in a magnetic pulse compression circuit showed that the Fe-based nanocrystalline soft magnetic alloy was the best core material for a compact switch with low core loss. At a 10 Hz repetition rate the maximum output energy obtained in a 80/spl times/60 nm discharge cross section and in 70 ns pulses (FWHM) was 6.2 J.

Magnetic Properties and Microstructures of Nanocrystalline Fe-M (M=Y,Ce)-O Films

Recently, Fe-based nanocrystalline soft magnetic alloys with a high saturation magnetization B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> , produced by melt-spinning and sputtering, have been discovered. Most of these alloys are obtained by annealing an amorphous phase, and consequently there is a limit to the B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> imposed by glass-forming materials. We have been studying soft magnetic alloy films with high B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> , which have nanocrystalline structures in the as-deposited state. In this paper, we describe the magnetic and structural properties of nanocrystalline Fe-M-O (M=Y,Ce) alloy films. The Y or Ce and O elements in the films tend to make the bcc grains finer in the as-deposited state, and also repress the growth of grains during annealing through the presence of very fine (less than 10 nm in size) oxide particles containing Y or Ce. The highest B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> and μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> values at 1 MHz, and the lowest H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> value, were 1.95 T, 1200 and 0.6 Oe respectively for a Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">85</sub> Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> film annealed at 773K for one hour.