Magnetic Properties Of Nanocrystalline Alloys Research Articles

Enhanced soft magnetic properties in high-Ms Fe-B-Si-C-Cu-Nb alloys: Mitigated surface crystallization and controlled nanocrystallization via optimized metalloid content

The study investigated the impact of the boron/silicon ratio on the soft magnetic properties and surface crystallization of nanocrystalline Fe80(BaSib)15C1Cu1Nb3 (a:b, a=1–6, b=1,0) alloys. The addition of boron and silicon also enhances glass forming ability and nanocrystal formation, thereby affecting the magnetic properties of nanocrystalline alloys. Observations revealed variations in the glass forming ability based on the ratio, and the occurrence of surface crystallization and its adverse effects on magnetic properties were examined in alloys with inadequate amorphous formation. In subsequent experiments the iron content was increased to boost the saturation flux density after identifying the optimal ratio. The results highlighted that deficiencies in glass forming ability lead to surface crystallization. In conclusion, the results of the experiment yielded an optimal boron/silicon ratio of 5:1, showcasing magnetic properties with a coercivity of 14.7 A/m and a magnetic flux density of 1.62 T. Compared to alloys with different ratios, superior magnetic properties and reduced surface crystallization were achieved.

Nanostructural evolution and improved magnetic performance of high saturation-induction Fe-based alloy via two-step combination crystallization

Refining nanoparticles and reducing the average random anisotropy constant (<K1>) are crucial for improving the magnetic properties of nanocrystalline alloys with high magnetic saturation induction. This study systematically investigates the evolution of nanostructure and soft magnetic performance during two-step combination annealing, which includes stress annealing at a flash heating rate followed by normal-annealing. Stress-annealing at 500 °C prior to crystallization reduces the area of the FeB-like short-range-order structure and effectively increases the number density of Cu clusters that act as heterogeneous nucleation sites for α-Fe(Si) nanoparticles. Stress-annealing at 500 °C precipitates tiny (∼ 5 nm) Fe3Si nanoparticles (A6 structure) dispersed in an amorphous matrix, resulting in more Fe clusters in the amorphous matrix and superior crystallinity following the second-step annealing process. The two-step combination annealing process increases the magnetic saturation induction (by ∼3%) and permeability (by∼62%) at 10 kHz in comparison with those obtained for the one-step annealed sample. Moreover, we propose a model for nanostructural evolution and the observed correlation with magnetic performances.

Measurement and Simulation of Magnetic Properties of Nanocrystalline Alloys under High-Frequency Pulse Excitation

In order to broaden the application of nanocrystalline soft magnetic materials in electrical engineering under extreme conditions, nanocrystalline alloys must also have good characteristics under high-frequency and nonsinusoidal excitation. In this paper, the magnetic properties of Fe-based nanocrystalline alloys excited by high repetition frequency pulses were measured. Excitation frequency and duty cycles are two important factors in the study of magnetic properties under pulse excitation. With the amplitude of the pulse remaining constant, different local hysteresis curves were obtained by changing the frequency and duty cycle. The experimental results proved that the higher the frequency is and the smaller the duty cycle is, the narrower the local hysteresis loop is. Finally, the finite element method (FEM) was used to model the magnetic core coupling with an impulse circuit based on the measured magnetic properties. Compared with the experimental results, the simulation results showed that the field-circuit coupling analysis model can effectively reflect the influence law of the frequency and duty cycle on magnetic properties.

Design issues of Rotational Single Sheet Tester for Fe-Based Nanocrystalline Alloys at High Frequencies

Measuring the vector magnetic properties of nanocrystalline soft magnetic materials at high frequencies is of great significance to the optimal design and energy saving of the electrical equipment. In this paper, some key design issues are discussed for a rotational single sheet tester (RSST) to further studied the Two-Dimensional (2D) magnetic properties of nanocrystalline alloys in the kilohertz range. Firstly, the magnetization uniformity of the testing sample is analyzed and discussed considering the stray field. Secondly, the magnetizer

The Effect of B and Si Additions on the Structural and Magnetic Behavior of Fe-Co-Ni Alloy Prepared by High-energy Mechanical Milling

Nanocrystalline Fe50Co25Ni15X10 (X = Bamorphous, Bcrystalline, and Si) powdered alloys were prepared by mechanical alloying process. Morphological, microstructural, and structural characterizations of the powders milled several times were investigated by scanning electron microscopy and X-ray diffraction. The final crystallographic state strongly depends on the chemical composition and the grinding time; it can be single-phase or two-phase. The crystallite size reduction down the nanometer scale is accompanied by the introduction of high level of lattice strains. The dissolution of Co, Ni, B (amorphous and crystalline), and Si into the α-Fe lattice leads to the formation of highly disordered Fe-based solid solutions. Coercivity (Hc) and the saturation magnetization (Ms) of alloyed powders were measured at room temperature by a vibration sample magnetization. The magnetic measurements show a contrasting Ms and (Hc) in all alloy compositions. Conclusively, soft magnetic properties of nanocrystalline alloys are related to various factors such as metalloid addition, formed phases, and chemical compositions.

Design of Novel High-Frequency 2-D Magnetic Properties Tester for Nanocrystalline Alloy

To broaden the applications of promising nanocrystalline magnetic materials in electrical engineering at high frequency, the materials must be characterized well at a wide range of frequencies and fields. This paper proposes a novel two-dimensional (2-D) magnetic properties tester up to 20 kHz. The finite element method is used to optimize the tester design by calculating the magnetic field distributions in the specimen and yokes. Considering the dimension and physical properties of the specimen, a particular B - H sensing structure is designed to measure the flux density and field intensity in the specimen. Furthermore, a frequency-domain feedback control system is integrated into the measurement system in order to control the waveform of flux density. Moreover, the paper discusses the factors which impact on the experimental results. This paper demonstrates that the novel tester is reliable to study the magnetic properties of materials. At last, the 2-D rotational magnetic properties of nanocrystalline alloy are preliminary measured.

Effect of Magnetic Pulsing and Low-Temperature Vacuum Annealing on the Soft Magnetic Properties of Hitperm Amorphous/Nanocrystalline Alloy

We studied soft magnetic properties of FeCoHfBCu amorphous/nanocrystalline alloy treated by medium-frequency magnetic pulsing (frequency 1500-2000Hz, field intensity 200-250Oe) and vacuum annealing at low temperature. The results of Mössbauer spectroscopy and transmission electron microscope show that the treating of magnetic pulsing with a medium frequency can introduce the nanocrystallization of amorphous FeCoHfBCu, precipitation of nm phase α-Fe(Co). And, with the increasing of pulsed frequency and field itensity, the crystalized volume friction increases from 24.71% to 35.2%. The low-temperature vacuum annealing for 100°C/30min of magnetic pulsed samples further improved the soft magnetic properties of nanocrystalline alloy. As compared with the amorphous state, the magnetic coerelvity decreaced from 103.4A/m to 34.0A/m, the saturated magnetization decreased from 160.47emu/g to 149.32emu/g.

Characterisation of high-anisotropy nanocrystalline alloys based on magnetic susceptibilities in the remanent state

The macroscopic magnetic properties of nanocrystalline alloys are strongly dependent on microstructural and micromagnetic inhomogeneities along with intergranular interactions. In particular, magnetic susceptibility is sensitive to these factors and frequently used for alloy characterisation. In this work reversible magnetic susceptibility in the remanent state of the nanocrystalline alloy with randomly oriented easy magnetisation axes is considered. Due to intergranular interactions the susceptibilities measured parallel and perpendicular to the remanence can be distinctly different from each other. When the intergrain exchange is the dominant interaction this susceptibility feature has potential for its quantitative evaluation. Here this opportunity is studied by means of two approaches: analytical solutions based on the mean-field approximation and simulations using the kinetic Monte Carlo model. The dependence of the magnetic susceptibility on the exchange coupling strength are investigated taking into account the effects of grain size distribution and magnetostatic interactions. These results lead us to propose an experimental susceptibility-based method for the estimation of both intergrain exchange interaction strength and effective magnetic anisotropy constant. This method can be used for the characterisation of high-anisotropy nanocrystalline alloys with randomly oriented easy magnetisation axes that is a widespread case. The method is applied to rapidly quenched Nd2(Fe0.8Co0.2)14B nanocrystalline alloy giving strong exchange coupling and a reasonable value for the anisotropy constant.

Characterization of magnetic properties of nanocrystalline alloys under rotational magnetization

Due to lacking the measurement results of magnetic properties under rotational magnetization, the application of nanocrystalline alloys for high-power system energy conservation has been limited. In this paper, a high-frequency rotational magnetic property testing system is first introduced. Base on the testing system, the rotating loci of the vector magnetic flux density B and the vector magnetic field strength H are measured. Finally, the rotational core loss and anisotropy of nanocrystalline alloys are discussed and analyzed.

Characterization and assessment of the wideband magnetic properties of nanocrystalline alloys and soft ferrites

Abstract

Optimization of crystallization, microstructure and soft magnetic properties of Fe-B-Cu alloys by rapid cyclic annealing

Fe83.5B16.5-xCux (x = 0, 0.7, 1.2, 1.5) amorphous alloys were rapidly annealed under various cyclic numbers (C). The crystallization behavior and its effects on the microstructure and soft magnetic properties of nanocrystalline alloys have been investigated. It is found that the cyclic annealing is more effective to refine and uniform α-Fe grains by introducing multiple rapid heating than the non-cyclic annealing. The saturation magnetic flux density of the Fe83.5B15Cu1.5 nanocrystalline alloy increases from 1.79 T to 1.82 T and the coercivity decreases from 13.1 A/m to 7.5 A/m simultaneously when the cyclic numbers change from C = 1 to 6. Moreover, the rapid cyclic annealing with C = 6 enlarges the annealing temperature ranges for the Fe83.5B16.5 and Fe83.5B15Cu1.5 nanocrystalline alloys with low HC by ∼20 K compared to that with C = 1. The Mössbauer spectroscopy confirms that the rapid cyclic annealing can inhibit the aggregation of B atoms in the amorphous matrix, which is beneficial to enhance the magnetic interaction between α-Fe nanocrystals. However, when the cyclic numbers further rise to C = 10, the mean grain size of the Fe83.5B15Cu1.5 nanocrystalline alloy begins to increase, resulting in the deterioration of soft magnetic properties.

Effect of Inhibitors on the Crystallization and Magnetic Properties of Nanocrystalline Alloys

In the paper, the crystallization process of nanocrystaline alloys Fe73.5Cu1M3Si13.5B9 where M = Nb, W, Mo, V, Cr and the physical origin of different efficiency of impact that inhibitors exert on the structure and magnetic properties has been investigated. It is shown that the structure formed at the peak temperature of the crystallization process is close to the optimal one and ensures high values of magnetic permeability. The efficiency is directly related to the solubility of inhibitory elements in αFe, which in turn affects the diffusivity of atoms. Upon slow migration of grain boundaries, the inhibitory atoms with lower diffusivity, being concentrated near the front of moving boundary, provide stronger drag.

Waveform Conditioning Problems of Nanocrystalline Alloys Under One/Two-Dimensional High-Frequency Magnetization

The problem of waveform distortion in high-frequency magnetization of nanocrystalline alloys has been discussed and analyzed in this paper. By measuring the sample in a rotational single sheet tester, the distortion caused by the dc bias field is largely reduced. A robust control algorithm based on model-free control is developed to keep the magnetic flux density sinusoidal when the materials are magnetized to saturated at high frequencies. Finally, the vector magnetic properties of nanocrystalline alloys are measured after adjusting the waveforms. The losses from 2 to 10 kHz in the casting direction and the transverse direction are calculated and compared.

Magnetic Properties of Nanocrystalline Alloys after Electrons Irradiation

Magnetic Properties of Nanocrystalline Alloys after Electrons Irradiation

A New Magnetizer for Measuring the Two-Dimensional Magnetic Properties of Nanocrystalline Alloys at High Frequencies

Nanocrystalline alloys are used extensively in high-frequency electromagnetic applications for their low magnetic losses and high saturation flux densities. To characterize their vector magnetic properties over a broad frequency range, a new magnetizer with a compact flux density-field B-H sensor was developed for two-dimensional testing up to 10 kHz.

Measurement of rotational magnetic properties of nanocrystalline alloys by a modified B-H sensor

Nanocrystalline alloys are now widely used in high frequency electromagnetic applications such as high frequency transformers and chokes, while it’s two-dimensional properties are seldom investigated. The nanocrystalline sample can be extremely brittle after annealed and crystallized which is very difficult to measure the properties by traditional method in 2D cases. The magnetic properties of nanocrystalline alloys under rotating field are measured and discussed in this paper. By combining the needle probe technique and the H-coil method, the magnetic flux density B and the magnetic field strength H in the sample can be measured. Finally, the modified B-H sensor is calibrated by the Helmholtz coils and the sensitivity of measuring B and H can achieve 4.3 mV/T and 30 μV/A/m respectively.

Low-Temperature Annealing on Treated of Pulsating Magnetic Field Fe-Co-M-B-Cu Amorphous

After the medium-frequency magnetic pulse treating (frequency 1500-2000Hz, field intensity 200-250Oe) on amorphous Fe (Co)-M-B-Cu alloys, the vacuum anealing at low-temperature were in progress at 50°C-100°C for 30 min and 60 min. The soft magnetic properties of nanocrystalline alloy obtained by above mentioned treatments were measured by the vibrational specimen magnetometer. The results show that the structral relaxation , free volume migration and annihilation during the vacuum annealing will lead to the reduction of like-vacancy defects concentration and distortion stress. So the soft magnetic properties of nanocrystalline alloy will be improved further.

EFFECT OF LOW-TEMPERATURE VACUUM ANNEALING ON THE MAGNETIC PULSED AMORPHOUS Fe 52 Co 34 Hf 7 B 6 Cu 1 ALLOY

The nanocrystalline Fe52Co34Hf7B6Cu1 soft magnatic alloys composed of bcc-Fe nanocrystals embedded in a residual amorphous matrix were obtained by the magneto-crystallization of melt-spun ribbons. In order to improve the soft magnetic properties of double-phase Fe(Co)-based nanocrystalline alloy, the nanocrystalline alloy specimens were vacuum annealed for 30 min at 100, 200 and 300 . The results showed that the treatment of magnetic pulsing on the amorphous alloy resulted in the nanocrystallization, the grain size of precipitated α-Fe(Co) nanocrystallized phase was 5—10 nm. The low-temperature vacuum annealing of magnetic pulsed specimens further improved the soft magnetic properties of nanocrystalline alloy. The influence of annealing at 100 for 30 min on the properties is most obvious.

Structure and magnetic properties of nanocrystalline alloys based on (Fe, Co)3O4

X-ray structural analysis, scanning and transmission electron microscopy methods are used to study the structure of nanocrystalline alloys prepared by grinding a mixture of FeO and Co powders in a high-energy mill followed by low-temperature annealing. Magnetic properties of the powders are measured in a vibration magnetometer at room temperature.

Corrosion of Fe-Based Nanocrystalline Alloys with Soft Magnetic Properties

Abstract Iron-based nanocrystalline alloys have attracted increasing attention due to their good soft magnetic properties for industrial applications. These alloys combine low magnetic loss, high saturation magnetic flux density, low coercive force, and high permeability, which are important in soft magnetic materials applications. Corrosion not only decreases the service life of soft magnetic materials, creating the need for system replacement, but can also damage the soft magnetic properties of these alloys. This behavior can lead to serious consequences in several applications, e.g., when solenoid valves or magnetic sensors are used for controlling combustible fluids or pressure vessels. Therefore, in the past few years, considerable interest has focused on the effect of microstructure and composition on the corrosion of iron-based amorphous and nanocrystalline alloys and on the effect of corrosion on the magnetic properties of these materials. This paper describes the main families of nanocrystalline Fe-based alloys with soft magnetic properties and discusses their magnetic properties and applications. In addition, the effect of partial crystallization on corrosion resistance is examined, including a critical discussion about the mechanisms reported in the literature. Other points analyzed here are the relationship between nanocrystalline alloy corrosion and composition, the effect of main alloying elements such as Nb, Zr, and No, the effect of corrosion on the magnetic properties of nanocrystalline alloys, and trends for future investigations. The aim of this paper is to review the current body of knowledge about the corrosion of nanocrystalline Fe-based alloys with soft magnetic properties and to highlight the importance of corrosion on the behavior of nanocrystalline soft magnetic materials.