Saturation Magnetic Flux Research Articles

Influence of Ge doping on the magnetic properties and microstructure of Fe-Si-B-P-Cu alloys prepared with industrial raw materials

With the increasing demand for energy efficiency and miniaturization, there is a growing need for magnetic materials with high saturation magnetic flux density (Bs) and low coercivity (Hc). Here, Fe82.3Si4B9P4-xCu0.7Gex (x = 0, 1, 2) nanocrystalline ribbons were prepared using industrial raw materials (IRMs). We found that appropriate Ge doping can optimize Bs by enhancing the crystallization volume fraction of α-Fe phase, and refine grain size by increasing the energy barriers for the growth of α-Fe and Fe(B, P) phases, which ultimately reduces Hc. However, Ge doping can also induce surface crystallization of the ribbons due to the enrichment of Cu elements. Excessive diffusion of Cu into the crystalline layer is not favorable for grain refinement, which deteriorates the soft magnetic properties of the ribbons.

Analytical Approach for Estimating the Average Torque of Synchronous Motors by Using the Flux Density in the Air Gap

In this study, a generalized torque estimation method is proposed for synchronous motors, including surface permanent magnet synchronous motors (SPMSMs), synchronous reluctance motors (SynRMs), and interior permanent magnet synchronous motors (IPMSMs) for building the analytical motor model. The average motor torque is estimated using the Lorentz force by the generated flux density in the air gap to determine the relationships among torque, flux density, and injected current. In the proposed method, the generated flux density is derived step by step by considering the effects of magnetic flux saturation, the stator slot, the rotor barrier, and permanent magnets (PMs) to ensure that the generated average torque complies with the operating condition of the motor. To verify the proposed method, the output torque of finite element analysis (FEA), Maxwell 2D, is compared to the proposed method in a SPMSM. Moreover, a phasor diagram is plotted to determine the mechanism through which torque is generated in SynRMs and IPMSMs. A SynRM and an IPMSM with ferrites PMs are analyzed using the proposed method, FEA, and the experimental results of this study indicate the effectiveness.

Efficient property-oriented optimization of magnetic high-entropy metallic glasses via a multi-stage design strategy

High-entropy metallic glasses (HE-MGs) have drawn much attention as promising multifunctional materials combining the excellent soft magnetic properties of traditional metallic glasses and impressive mechanical properties, thermal stability, corrosion resistance, etc., of solid solution high entropy alloys. Property optimization of HE-MGs is of great significance for promoting their engineering applications. However, various constituent elements and the high chemical complexity make the possible alloying composition space extremely massive, which is very challenging for the rational design of HE-MGs. In this work, we proposed a multi-stage optimization strategy based on machine learning (ML) to accelerate the rational design of magnetic HE-MGs with desired properties. The huge composition search space was significantly narrowed by the ML-based phase prediction model and constraints from user preferences. Utility functions based on the exploitation and exploration strategy were designed to find the global optimization solutions, i.e., alloying compositions. Experiments were conducted as concept validation, and new Fe-Co-Ni-Si-B HE-MGs with balanced saturation magnetic flux density and mixing entropy were developed.

Structure evolution and magnetization properties of FeSiBCCr amorphous alloys prepared by spark plasma sintering

FeSiBCCr bulk metallic glasses were prepared via spark plasma sintering, and the effects of holding time and heating rate on the structure and magnetization properties of powder compacts were investigated by SEM, TEM, XRD, DSC and VSM. The results show that when the holding time is increased from 10 min to 20 min, the internal porosity is reduced, and the amorphous fraction is decreased from 92.0 ± 1.7 % to 82.4 ± 4.3 % accompanied by the precipitation of fine nanocrystalline grains. When the holding time is increased to 30 min, the precipitation of the ferro-boron phase and growth of nanocrystalline grains lead to a significant deterioration of magnetization properties, although the compact density is significantly increased to 6.13±0.12 g/cm3. When the heating rate is increased from 20 K/min to 100 K/min, the activation energy of viscous flow is decreased and the compact density is improved due to the enhanced mass transfer. Moreover, the thermal stability of the amorphous material is also improved, effectively suppressing the grain coarsening and the precipitation of the ferro-boron phase. As a result, the saturation magnetic flux density is increased by 10 % and the coercivity is reduced by 83 %. The FeSiBCCr bulk metallic glasses prepared at a sintering temperature of 773 K, a heating rate of 100 K/min, and a holding time of 10 min contain an amorphous matrix with fine Fe2Si grains. And the compact has a density of 5.60±0.08 g/cm3, a saturation magnetic flux density of 1.03±0.03 T, and a coercivity of 15.9 ± 1.2 A/m, exhibiting promising magnetization properties and being expected to be used in medium and high frequency electronics.

Improvement of soft magnetic properties of a Nanoperm-type Fe-Hf-B nanocrystalline alloy upon surface crystallization inhibition by Cu addition

Nanoperm-type alloy ribbons suffer from surface crystallization during melt spinning, which degrades their magnetic properties after annealing and limits their commercial application. Here, we investigate the effects of Cu addition on the structure and magnetic properties of a surface-textured Fe87-xHf5B8Cux alloy. Adding Cu (1 ≤ x ≤ 2) removes the surface coarse grains in the free surface of the melt-spun precursor, while induces the precipitation of large amounts of the α-Fe nanoparticles with ∼3 nm in size, which contributes a homogeneous ultrafine structure and improved magnetic softness after annealing. The grain size, coercivity, saturation magnetic flux density, and effective permeability at 1 kHz of the Fe86Hf5B8Cu1 nanocrystalline alloy are 13.3 nm, 6.6 A/m, 1.68 T, and 23000, respectively, whereas these are 16.0 nm, 16.8 A/m, 1.70 T, and 15000, respectively, for the Fe87Hf5B8 alloy. The Cu-improved effect is mainly attributed that Cu induces heterogeneous nucleation of the α-Fe phase to strengthen the competitive growth among grains.

Effects and mechanisms of Nb and Fe additions on glass-forming ability and magnetic properties of a Co71.5Gd3.5B25 metallic glass

Aiming to unraveling the effects and mechanisms of Nb and Fe additions on glass-forming ability (GFA) and magnetic properties, especially coercivity (Hc) on Co-based metallic glasses, 2–4 at% Nb and/or 7.15–28.6 at% Fe have been alloyed into a Co71.5Gd3.5B25 alloy by substitution of Co. The results show that alloying either Nb or Fe into the base alloy leads to enhanced stability of supercooled liquid and GFA, and bulk metallic glass (BMG) can be formed for the alloy with 4 at% Nb or 28.6 at% Fe. Combined addition of Nb and Fe further improves the thermal stability and GFA, and lowers viscosity in supercooled liquid state. A (Co0.6Fe0.4)67.5Gd3.5Nb4B25 BMG possess a wide supercooled liquid region (ΔTx) of 85 K, critical sample diameter of 3.0 mm, and minimum viscosity coefficient of 2 × 108 Pa∙s. The enrichment of Fe increases saturation magnetic flux density (Bs), Hc, and saturation magnetostriction coefficient (λs) of the (Co, Fe)-Gd-B-(Nb) metallic glasses; the addition of Nb effectively inhibits the deterioration of magnetic softness caused by Fe while reducing the Bs. The (Co0.6–0.9Fe0.1–0.4)67.5Gd3.5Nb4B25 BMGs possess good soft magnetic properties with the Bs and Hc ranging 0.43–0.69 T and 2.3–5.0 A/m, respectively. Ab initio molecular dynamics simulations indicated that alloying Fe into the Co-based metallic glasses leads to enhanced magnetic anisotropy energy. The increased magnetic anisotropy arising from enlarged λs results in the increased Hc. The combination of high GFA, large ΔTx, low viscosity, and good soft magnetic properties makes the Co-based Co-Fe-Gd-Nb-B BMGs highly promising for applications as micro electromagnetic devices produced through thermoplastic forming.

Formulation and mixing conditions of magnetic composite materials used for magnetic wedges in an interior permanent magnet synchronous motor

AbstractAn interior permanent magnet synchronous motor (IPMSM) is characterized by its high efficiency. However, torque ripple and loss occur because of the spatial harmonics generated by air‐gap permeance fluctuations. This study clarified that slot harmonic components can be suppressed by inserting magnetic wedges made of magnetic composite material in the slot opening of an IPMSM. First, the authors examined the torque and loss characteristics by varying relative permeability and saturation magnetic flux density of magnetic wedges using finite element analysis (FEA). Results indicated that the torque ripple and loss could be suppressed when the relative permeability of the magnetic wedge was μr = 10 to 22 and the saturation magnetic flux density was Bs = 0.5 to 0.75 T. Furthermore, the authors produced magnetic composite materials made of various soft magnetic material powders and examined their magnetic properties and viscosities. Results showed that a magnetic composite material with optimal magnetic properties and injectable viscosity could be manufactured using Fe‐Si‐Al with a low volume fraction.

Effects of B/P and Co/Fe substitutions on glass-forming ability and soft magnetic properties of a Fe80P13C7 metallic glass

New soft magnetic Fe-based Fe–Co–P–B–C bulk metallic glasses (BMGs) with the highest saturation magnetic flux density (Bs) up to 1.68 T among current Fe-based BMGs have been developed. Initial replacement of P by 2–6 at.% B enhances the thermal stability, glass-forming ability (GFA), and soft magnetic properties of a Fe80P13C7 alloy. A Fe80P9B4C7 BMG with a supercooled liquid region of 38 K, Bs of 1.63 T, and coercivity (Hc) of 0.9 A/m has been obtained by copper mold casting. Substitution of Fe by 5–10 at.% Co in the Fe80P9B4C7 alloy further enhances the GFA and Bs, but leads to a moderate increase in Hc. A critical sample diameter of 1.5 mm, Bs of 1.68 T, and Hc of 6.2 A/m can be achieved for a Fe70Co10P9B4C7 BMG. The improvement of the GFA is attributed to the enhanced stability of alloy melts achieved by similar B/P and Co/Fe substitution.

Structural heterogeneity, β relaxation and magnetic properties of Fe-Zr-B amorphous alloys with Si and Cu additions

Despite numerous studies on β relaxation of amorphous alloys, the relationship between structural heterogeneity and β relaxation and the effect on magnetic properties of Fe-based amorphous alloys is still unknow. In this work, the structure and magnetic properties of Fe84-xZr6B10Mx (M = Si, Cu; x = 0, 0.6, 1 at%) amorphous alloys were investigated. With the increase of Si content, the negative value of average chemical affinity (∆Hchem) of the alloys is increased, leading to the synergetic enhancement in structural heterogeneity and β relaxation. In addition to this, the increase of liquid-like regions (LLRs) reduces saturation magnetic flux density (Bs) and increases coercivity (Hc). However, the addition of Cu element decreases the negative value of ∆Hchem of the alloys, resulting in weakening of structural heterogeneity and β relaxation synergetically. The reduction of LLRs has resulted in increase in Bs. Moreover, Fe-Cu atom pairs with positive enthalpy of mixing increases the local density of quasi dislocation dipoles (QDDs), resulting in the increase of Hc.

Affable thermal treatment process to overcome the trade-off relation via interface engineering in an Fe-based amorphous film

As pre-eminent soft magnetic materials, Fe-based amorphous alloys have been extensively studied due to adjustable composition, low cost, and low iron core loss. The soft magnetic properties could be further improved after thermal annealing, which achieve a low coercive force (Hc) due to the low magnetic anisotropy and a high saturation magnetic flux density (Bs) on account of the precipitation of soft magnetic nanocrystalline phases. However, it is a key difficulty to control the nucleation and growth procedures of nanocrystals during annealing, resulting in rapid deterioration of Hc. Here, a soft magnetic Fe76Si8B13Nb3 film with ultra-fine amorphous/crystalline (a/c) core–shell structure is achieved from an amorphous precursor with the nanoscale phase separation. The pre-existing nanoscale phase separation provides vast nucleation sites and interphase boundaries, which could generate high concentration of nanocrystals and depresses the subsequent coarsening behavior even for long-time heat treatment. In consequence, the a/c core–shell soft magnetic film breaks the general trade-off relation in the soft magnetic material family with the highest Bs and lowest Hc simultaneously. This work provides a new perspective to design a/c alloys by amorphous precursor with dual phase structure, and importantly, it supplies effortless thermal treatment requirement to conveniently regulate the microstructures and soft magnetic properties of metallic glasses.

Iron Losses Comparison of Two Kinds of Permendurs under Rotating Magnetic Flux Density Conditions

Vector magnetic properties of permendurs have been investigated by using a vector magnetic property measurement apparatus to select a magnetic material suitable as a motor core material. When a motor is rotated at high speed by high-frequency excitation to increase power of a motor, a magnetic material with a high saturation magnetic flux density and a low iron loss is useful for a motor core. However, iron loss versus frequency characteristics under rotating magnetic flux density conditions of permendurs have not been sufficiently investigated. Moreover, the magnetic characteristics of permendurs made by different manufacturers have not been compared. Therefore, in this paper, the vector magnetic properties under rotating magnetic flux density conditions of two kinds of permendur made by different manufacturers are measured and compared for iron losses.

A comparison study between the optimal DFIG flux and speed control in presence of magnetic hysteresis and classical control strategies for wind systems

In the wind energy systems field, the most common control objective treated by authors is the speed and flux control of the doubly fed induction generator (DFIG). For computing complexity matter, the generator mathematical representation is generally modelled assuming a linear magnetic characteristic. Based on this assumption, the rotor flux control will aim to track a fixed flux reference, mostly its nominal value. The inconvenience with this strategy is that practically, neglecting the nonlinearity of the generator’s magnetic characteristic, optimal performance control cannot be performed. In this study, considering the magnetic flux hysteresis and saturation characteristic, new modelling of the DFIG is presented. Furthermore, a new speed and optimal flux Backstepping controller is designed based on the Lyapunov theory. To prove its performance, a comparison study with different control strategies will be conducted. Simulations considering a wide range of wind speed variations are illustrated in the Matlab/Simulink environment.

Origin of the improved Bs for Fe-Si-B-Mn microalloyed amorphous alloys

In this study, the saturation magnetic flux density (Bs) and the local structure of Fe80Si9-xB11Mnx (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0 at.%) amorphous alloys are investigated. The optimum addition of 0.3 at.% Mn on Bs results from the strengthening of ferromagnetism with larger interatomic distance of Fe. However, excess Mn addition will result in the antiferromagnetic coupling between Mn and Fe atoms, which in turn leads to the decrease of Bs. A model has been proposed to evaluate the optimum doping content of Mn for the highest Bs by calculating the fraction of amorphous pure Fe with average magnetic moment of 0.40 μB and the coordination number of one Mn solute. The present work is promising to provide a guideline for choosing the content of the minor alloying on improving Bs of Fe-Si-B amorphous system.

Connecting the composition, structure, and magnetic property in high-entropy metallic glasses

High-entropy metallic glasses (HE-MGs) are a new class of materials with unique properties that often exceed both those of crystalline high-entropy alloys and single-principal-element metallic glasses. In recent years, soft magnetic HE-MGs have shown excellent glass-forming ability and superb magnetic softness, thus exhibiting promising prospects. However, the lack of a sufficient understanding of composition-structure-property relationships is a major challenge for the development of HE-MGs. Here, we propose the "framework + fluctuation" model based on the Bethe-Slater (BS) curve. The model shows that in HE-MGs, metalloids will change the distribution of ferromagnetic metal atoms in the short-range (interatomic) length scale, thus affecting Curie temperature (TC) and saturation magnetic flux density (Bs) of HE-MGs. The model explains the dramatic variation of Bs caused by changing the ratio of metalloids in HE-MGs with a fixed content of ferromagnetic metal elements. The structural changes predicted by the model were further confirmed by ab initio molecular dynamics simulations. Besides providing a theoretical explanation, the model also quantitatively characterizes the effects of different metalloids on both structure and magnetic properties. The model sheds light on the role of the short-range distribution of ferromagnetic metal elements on ferromagnetism in HE-MGs, providing insights into the development of high-performance soft magnetic HE-MGs.

Measurement and Analysis of Magnetic Properties of Permalloy for Magnetic Shielding Devices under Different Temperature Environments.

The relative permeability, coercivity, and remanence of permalloy are closely related to the performance of magnetic shielding devices. In this paper, the relationship between the magnetic properties of permalloy and the working temperature of magnetic shielding devices is measured. Firstly, the measurement method of permalloy properties based on the simulated impact method is analyzed. What is more, a magnetic property test system consisting of a soft magnetic material tester and a high-low temperature chamber for permalloy ring samples at different temperatures was established to measure DC and AC (0.01 Hz to 1 kHz) magnetic properties at different temperatures (-60 °C to 140 °C). Finally, the results show that compared with room temperature (25 °C), the initial permeability (μi) decreases by 69.64% at -60 °C and increases by 38.23% at 140 °C, and the coercivity (hc) decreases by 34.81% at -60 °C and increases by 8.93% at 140 °C, which are the key parameters in the magnetic shielding device. It can be concluded that the relative permeability and remanence of permalloy are positively correlated with temperature, while the saturation magnetic flux density and coercivity are negatively correlated with temperature. This paper is of great significance to the magnetic analysis and design of magnetic shielding devices.

Convolutional neural network guided prediction of saturation magnetic flux density of Fe-based metallic glasses

Fe-based metallic glasses (FeMGs) have recently garnered considerable research attention due to their unique characteristics, such as low core loss and high saturation magnetic flux density (Bs). They also have promising applications in modern electrical machines, such as inductors, motors, and transformers. For FeMGs with high Bs, a trial-and-error approach using various metalloid elements as constituents has been intensively carried out to consider satisfactory thermal stability. However, this approach is time-consuming and expensive because it requires a huge compositional space and results in a lack of understanding of metalloid effects on magnetic properties and thermal stability. In this study, we established a deep learning model using a convolutional neural network (CNN) based only on compositional descriptors of FeMG constituent elements to predict Bs as the representative magnetic property. In addition, an artificial neural network was applied with the same compositional descriptors for comparison, resulting in a lower prediction performance than that of the CNN model. The CNN model demonstrated high-performance metrics that included a determination coefficient (R2) of 0.960 and a low root-mean-square error of 0.067 T, indicating that the material composition-to-property map is well-defined. We further applied the CNN model to unseen datasets for Bs prediction and compared it with results reported in the existing literature. The predicted Bs values are in excellent agreement with the reported experimental results.

Basic study on high precision positioning in electromagnetic valve drive system for improving internal combustion engine using linear actuator

In recent years, further improvements in the performance of internal combustion engines to reduce environmental burden have been demanded. The combustion state of an engine is affected by the parameters of the dynamic valve system, such as the opening/closing timing and the lift of the intake and exhaust valves. Therefore, we investigate an electromagnetic valve-drive system in this study. Two models are created to improve the magnetic circuit and increase thrust. To investigate the thrust characteristics of these actuators, an electromagnetic field analysis is conducted using the finite element method. Meanwhile, to investigate the effect of the yoke material on the thrust, an electromagnetic field analysis is performed based on materials with different saturation magnetic flux densities and magnetic permeabilities.

Wafer-Level Fabricated Tight-Coupling Dual-Solenoid Transformer Chips With Watt-Scale Power Transfer

Reported are a novel kind of tight-coupled dual-solenoid transformers (DSTs) which are on-chip integrated by using wafer-level fabrication including a low melting-point zinc-aluminum alloy rapid microcasting technique. Without magnetic core used, the silicon-chip integrated transformer is with the two metal solenoids tightly interwound to form a highly-coupled 3-D structure, thereby performing high inductance density and featuring no concern in magnetic flux saturation. Fabricated with the wafer-level thick-metal 3-D microcasting technique, the DST exhibits sufficient inductance value and low dc resistance while maintaining tiny footprint. Various DST structures are designed, fabricated and characterized for performance optimization. The optimally designed DST chip demonstrates a compact footprint of 2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , a high inductance of 193.14 nH (i.e., inductance density = 96.57 nH/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and a small dc resistance of 1.09 Ω. The test shows that the chip achieves an ultrahigh coupling coefficient of 0.95 and superior maximum transformer efficiency of 87.8% at 100 MHz. More importantly, the DST achieves <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Watt</i> -scale power transfer capability at 100 MHz, where no any heat dissipation treatment to the chip is used. Therefore, the on-chip DSTs are very promising for power/signal transmission in various electronic microsystems.

Effect of Mo addition on thermal stability and magnetic properties in FeSiBPCu nanocrystalline alloys

The glass forming ability, thermal stability, microstructure, and magnetic properties of Fe83.3(Si4B8P4)16−xCu0.7Mox (x = 0, 0.5, 1, and 1.5) alloys are studied to investigate the influence of Mo addition. With increasing Mo content, the negative mixing enthalpy (ΔHmix) increases and the Delta parameter (δ) decreases, which leads to a decline in the glass forming ability. The secondary crystallization temperature increases continuously with increasing Mo content. A small amount of Mo improves sufficiently the thermal stability of the alloy system, which can bear higher temperatures (up to 520 °C) for longer time (up to 40 min) without the formation of compounds because of their increased activation energy. The saturation magnetic flux density (Bs) decreases from 1.78 to 1.68 T with increasing Mo content as a result of the lower volume fraction of the α-Fe phase. Optimum magnetic properties with Bs = 1.74T and Hc = 8.2A/m are achieved in Fe83.3(Si4B8P4)15Cu0.7Mo1 ribbon.

(Fe-Ni)-based glassy alloy containing Nb and Cu with excellent soft magnetic properties

Magnetic properties of amorphous Fe38Ni38B12P5Si3Nb3Cu1 alloy ribbons have been investigated in as-spun and annealed states with the aim of developing an ultrasoft magnetic material which is expected to be used in advanced information data devices. A small amount of simultaneous addition of Cu and Nb to a FeNi-metalloid amorphous alloy system caused the change in crystallization process from eutectic type to the primary one. After annealing at the temperature just below the glass transition temperature (Tg), the glassy alloy ribbon exhibit excellent soft magnetic properties, very low coercive force of 1 A/m and extremely high effective permeability of 7.5·104 at 1 kHz which have not been obtained for any kinds of Fe- and Ni-based amorphous alloys, in spite of relatively low saturation magnetic flux density of 0.86 T. The further increase in annealing temperature causes the precipitation of nanoscale fcc particles with a size of about 7 nm including a high density of planar faults and the resulting nanostructure alloy also exhibits good soft magnetic properties with low Hc below 2 A/m. The formation of nanostructure fcc-(Fe,Ni) + glass soft magnetic alloys is also novel. The syntheses of the new Fe-Ni-based glassy and nanocrystalline [fcc(Fe,Ni) + glass] alloy ribbons with ultrasoft magnetic properties are encouraging as a new type of energy saving-type soft magnetic material.