Properties Of Soft Magnetic Materials Research Articles

The origin of good mechanical and soft magnetic properties in a CoFeNi-based high-entropy alloy with hierarchical structure

With the industry development, materials that combine good mechanical properties with new functional applications are in high demand. Here, a solution was provided to overcome low mechanical properties of soft magnetic materials through heterostructure design in CoFeNi high-entropy alloys (HEA). A CoFeNi-based HEA with a hierarchical structure with heterogeneous microstructure, consisting of body-centered cubic (BCC) bands, ultra-fine grained dual-phase and non-recrystallized lamellae (NRL) zones containing a high-density of nanoprecipitates, was fabricated and finely tuned by cold rolling (CR) and annealing. The HEA annealed at 850 °C (HEA-850) exhibits a noteworthy strength-ductility synergy than the counterparts with homogeneous dual-phase microstructures. The yield strength and elongation of the HEA-850 sample are nearly up to 1 GPa and 24%, respectively. Furthermore, because of the elimination of high-density dislocations, this alloy possesses good soft magnetic characteristics, and the saturation magnetization (Ms) and coercivity are 120 emu/g and 455 A/m, respectively. Detailed microstructure observations reveal that the high yield strength is mainly attributed to the interphase boundary strengthening from the dual-phase ultra-fine regions and nanoprecipitate strengthening as well as dislocation strengthening from NRL regions. Due to the mechanical and microstructural heterogeneity, multiple hetero-deformation induced hardening sustains persistent work hardening during tensile deformation, resulting in the reasonable ductility in the HEA-850 sample. The novel provides an important insight into developing high-performance materials with a superior combination of mechanical and functional properties using heterogeneous microstructure.

Research on the Magnetic Properties of High-Saturation Magnetically Induced Alloy Motors under Magnetocaloric Coupling.

In the face of the rapid development of the motor industry, some motors with traditional soft magnetic materials can no longer meet the needs of the market. Using new high-saturation magnetic density materials has become a new breakthrough to improve the torque density of motors. Fe-Co alloys (1J22) have high-saturation magnetic induction strength, which can effectively improve the motor's magnetic field strength and increase its torque density. At the same time, the temperature rise of the motor is also an important factor to consider in the motor design process. In particular, the change in core temperature caused by loss makes the coupling of the internal temperature field and the electromagnetic field of the motor more common. Therefore, it is necessary to test the temperature and magnetic properties of 1J22 together. In this paper, a coupling measurement device for magnetic properties of soft magnetic materials is built, and a 1J22 temperature field-electromagnetic field coupling experiment is completed. It is found that the maximum loss of 1J22 decreases by 4.44% with the increase in temperature; the maximum loss is 6.41% less than that of traditional silicon steel. Finally, a finite element simulation model is built to simulate the actual working conditions of the motor, and it is verified that the magnetic properties of the material at high temperature will have a certain impact on the performance of the motor.

Application of Amorphous and Nanocrystalline Soft Magnetic Materials in Balanced-Force-Type Electromagnetic Relay.

The magnetic properties of soft magnetic materials, including their saturation magnetic induction strength and permeability, significantly affect the dynamic characteristics of electromagnetic relays. However, the soft materials most commonly used for relays in the magnetic conductive components of electromagnetic systems, such as electrical pure iron, limit further relay design improvement and optimization to a certain extent. Thus, this paper proposes the use of amorphous and nanocrystalline soft magnetic materials with good high-frequency magnetic properties in magnetic circuits. A wavelet analysis was conducted on the high-frequency components of the coil current while the relay operated, and the corresponding magnetic materials were selected. Considering the challenges in processing amorphous and nanocrystalline materials and collecting test data for the accuracy verification of simulation methods, we prepared a scaled-up prototype for use in dynamic characteristic tests. The simulation method was improved, yielding more accurate simulation results regarding the relay's dynamic characteristics. On this basis, six replacement schemes using amorphous and nanocrystalline materials were considered. The test results proved that this application could improve the relay's dynamic characteristics. Finally, a full-size sample with an iron core consisting of nanocrystalline alloy 1K107B was prepared, and the conclusions were verified in tests.

Investigation of variety of valence metal ions combinated novel Co‐rich high entropy oxides and its magnetic properties and microstructure

In this work, a series of five spinel-structured oxides were synthesized using a straightforward and effective solid-state methodology. Departing from the conventional design concept, we opted for the substitution of Fe3 + with five metal cations, all possessing trivalent average valence states and equivalent proportions. X-ray diffraction, scanning electron microscope, energy spectrum analyzer, vibrating sample magnetometer were used to detect the phase, micro-structure, element distribution, magnetism of the samples, respectively. The test results show that samples have the spinel structure (Fd3(_)m), and the element composition and distribution are the same as expected. The test results of magnetic properties reveal that these five samples exhibit the properties of soft magnetic materials. The maximum adjustment range of saturation magnetization (Ms) is increased from 23.5 emu/g to 34.8 emu/g by adjusting the elemental composition. Besides, the maximum adjustment range of coercivity (Hc) is increased from 11 Oe to 60 Oe. Furthermore, these materials exhibit a low remanent magnetization ratio, indicating that high-entropy oxides with spinel structures are highly sensitive to changes in an applied magnetic field. The high-entropy oxide is a new material with great prospect. It creates new possibilities for the design of magnetic materials.

Measurement and analysis of magnetic properties under SVPWM excitation for soft magnetic composites (SMCs) and silicon steel

This study developed a system for measuring the magnetic properties of soft magnetic materials under space vector pulse width modulation (SVPWM) excitation, enabling testing at different modulation indexes, frequencies, and carrier frequencies. Two types of soft magnetic materials were tested, and the effects of SVPWM waveform parameters on material loss were analyzed. The results show that the loss of SMCs is higher than that of silicon steel when the max magnetic flux density is close to 1.5 T. In contrast, at the modulation frequencies are 100 Hz and 200 Hz, the loss of SMCs is lower than that of silicon steel. The reliability of the testing system was validated through magnetic characterization of the two materials, providing a reference for their application and preparation.

Effect of Magnesium Treatment on Cleanliness, Microstructure, and Magnetic Properties of Fe–80Ni Permalloy

Cleanliness and microstructure significantly impact the magnetic properties of soft magnetic materials. This study investigates the impact of Mg treatment on the cleanliness, microstructure, and magnetic properties of Fe–80Ni alloy. The content of Mg ranges from 0% to 0.034%. The O and S contents can be reduced to 0.0006% and 0.0011%, respectively, when the content of Mg is 0.027%, and the number of inclusions is reduced. Simultaneously, the primary inclusions are modified to Mg‐containing inclusions. Based on electron backscattered diffraction results, Mg treatment can refine the deformed grain and enhance grain boundary energy after cold rolling. In addition, the grains exhibit enhanced growth after annealing with Mg treatment. Due to the improvement of cleanliness and microstructure, the magnetic properties of Fe–80Ni alloy are enhanced with Mg treatment. With Mg treatment, the coercivity of alloys is reduced, and maximum magnetic susceptibility (χmax) increases to 0.3247 with Mg treatment, while that is 0.1938 without Mg treatment.

Concentration-dependent construction of raspberry-like SiO2 shell on spherical FeNi towards improved electromagnetic performance from kHz to GHz

Constructing resistive layer with novel structure holds great potential in upgrading electromagnetic properties of soft magnetic materials in a wide frequency range. In this work, FeNi@SiO2 composites with controllable core–shell structures, including 2D-type laminar shell and 3D-type raspberry-like shell, were fabricated by modified Stöber method. The structure of SiO2 shell depends highly on the concentration of tetraethyl orthosilicate (TEOS). In detail, a laminar shell can be formed at low TEOS concentration, owing to slow condensation. While at high TEOS concentration, heterogeneous growth on powder surface and homogeneous growth in solution of silica networks are significantly accelerated, resulting in the formation of the raspberry-like shell. Improved electromagnetic performance of FeNi@SiO2 cores at 2 MHz, including high resistivity, low eddy current loss, and low loss factor, should be ascribed to the unique raspberry-like shell structure. Meanwhile, raspberry-like shell also contributes to enhanced attenuation and acceptable impedance matching in GHz range. Consequently, a wide effective absorption bandwidth of 8.92 GHz can be achieved at a thin thickness of 1.85 mm. This work provides deep insights into the growth mechanism of different SiO2 shells and sheds new light on the design of high-performance soft magnetic composites working in different frequency bands.

Magnetic property measurement and analysis of high-frequency soft magnetic materials under non-sinusoidal excitation considering temperature effect

Electrical equipment operates under various temperatures and non-sinusoidal excitation, which makes magnetic properties of soft magnetic materials quite different from those under room temperature and sinusoidal excitation. Magnetic properties and loss characteristics of the ferrite (N87) and nanocrystalline alloy (FT-3KL) are measured and analyzed in the range of 25 °C to 125 °C from 5 kHz to 20 kHz under both square and rectangular excitation with different duty ratios. The temperature dependence of these materials under different conditions is systematically compared with normalization method. The comprehensive performance of core materials is discussed in combination with the experimental phenomena and results.

The microwave absorption properties of soft magnetic materials in frequency up to 40 GHz

With the continuous development of communication technology, the microwave frequency used has been extended to 24∼30 GHz or even higher. Thus, for the research on microwave absorption materials, the commonly used 2∼18 GHz frequency range might no longer be enough. More studies of microwave absorption properties in a higher frequency band are necessary. In this work, we report the microwave absorption properties of several soft magnetic composites in frequency up to 40 GHz. Magnetic materials such as iron, Y2Fe16Si, Ce2Fe17N3−δ, and La2Fe4Co10B micron powders which display excellent microwave absorption properties in 2∼18 GHz, are investigated. Within 2∼40 GHz, the reflection loss (RL) of iron/paraffin, Y2Fe16Si/paraffin, Ce2Fe17N3−δ/paraffin and La2Fe4Co10B/paraffin composites could reach −46.2 dB, −71.4 dB, −49.1 dB, and −40.1 dB, respectively. Moreover, their effective absorption bandwidth (RL < −10 dB) could reach 16.9 GHz, 8.53 GHz, 10.08 GHz, and 8.03 GHz, respectively. Though the measurements are extended to 40 GHz, the absorption properties of these composites become weak when the frequency rises to around 40 GHz, which is restricted by the cutoff frequencies of the materials. The measured data shows that these soft magnetic composites are good candidates for high-frequency microwave absorption materials, while exploring magnetic materials with further higher cutoff frequencies may result in better performance.

Sheet thickness dependence of magnetization properties based on domains and walls within the non-linear diffusion-like equation for grain-oriented electrical steels

The definition and development of a dynamic or transient magnetic formulation compatible with the Finite Element Method, able to take the dynamic hysteresis and classical and extra losses into account (not a posteriori but a priori), and using the most adapted state variable that makes the problem well defined and easily convergent requires the knowledge of dynamic behavioral properties of soft magnetic materials whatever the thickness and the working conditions. The dynamic hysteresis of soft magnetic materials corresponds to excess iron losses, due to dynamic magnetization reversal processes within magnetic domains and especially to microscopic eddy currents around the magnetic walls in motion and inside rotating domains. The model properties used are the internal quasi-static permeability μ and the dynamic magnetization property Λ that lumps the magnetization mechanisms (domain walls displacement, bowing, fusion, nucleation and multiplication). The latter are involved in the magnetic field damping due to microscopic eddy currents within the field diffusion that renders the magnetic behavior geometry dependent. This model does not separate the field diffusion process from the magnetization reversal mechanisms. In this paper, the sheet thickness ζ dependence of the dynamic magnetization property Λ(ζ) for a Grain Oriented Electrical Steel (GOES: steel made of 3% Silicon and Iron: SiFe) is analyzed in the Rolling Direction (RD). To this extend, it is proposed to carry out and interpret magnetic measurements on GOES samples with the Epstein frame for four different thicknesses (ζ = 0.23, 0.27, 0.30 and 0.35 mm), but with similar metallurgical and crystallographic properties for the whole specimens. Magnetic properties are first identified at low induction with linear assumptions and at higher induction with non-linearities. It makes it possible to re-compute the dynamic hysteresis loops of the material and to predict the losses whatever the working conditions with frequencies from 50 to 800 Hz. It is found that μ does not depend significantly on the sheet thickness whereas Λ depends on it significantly. Microscopic observation of the magnetic domains width are then performed thanks to the MOIF (Magneto-Optical Indicator Film) technique. It helps us discriminate between three simultaneous origins for the dependence of iron losses to the sheet thickness: a skin-like effect, a domains’ refinement and changes on the walls’ mobility. Results are discussed taking the dipolar magnetic effects, closure domains, the grains and texture and the manufacturing and coating residual stress on the metal surface into account.

Hierarchical geometric designs for Fe-based amorphous materials with tunable soft magnetic properties

Tailoring the soft magnetic properties of magnetic materials is highly desired from both academic and technological standpoints. In this study, we propose an alternative approach to manipulate the magnetic susceptibility and related properties of soft magnetic materials by geometric designs. For example, porous honeycomb structures of Fe92.9C3.5Si3.6 amorphous ribbons are fabricated with control over the wall width, which ranges from 60 to 130 μm. The magnetic field dependence of the magnetization shows that the magnetic susceptibility strongly depends on the wall width of porous honeycomb structures, i.e., the smaller the width, the higher the susceptibility. In addition, the susceptibilities of porous honeycomb structures are larger than that of their continuous counterpart. The geometrical dependence of the magnetic susceptibility is confirmed by phase field modeling. The simulation results suggest that a high density of domain walls can be accommodated in a porous honeycomb structure with a small wall width. Thus, the transitions of domain configurations under the magnetic field can be tailored, which brings about a geometrical dependence of the magnetic susceptibility. The present work opens a broad avenue for the geometric design of magnetic properties.

The thermodynamic properties of soft magnetic materials containing superparamagnetic nanoparticles frozen in the nodes of the regular cubic lattice

The thermodynamic properties of soft magnetic materials containing superparamagnetic nanoparticles frozen in the nodes of the regular cubic lattice

Enhancing Properties of Soft Magnetic Materials: A Study into Hot Isostatic Pressing and Sintering Atmosphere Influences

Soft magnetic materials are characterized by achieving a high magnetic induction value in the presence of a small magnetic field. Common applications of these materials, such as transformers or sensors, are in constant evolution and new requirements are becoming more demanding. Nickel and its alloys are employed as smart materials taking advantage of their superior magnetoelastic properties. A metal injection molding (MIM) technique provides high-quality complex-shaped parts with a good density and controlled impurity levels, which are necessary for these applications, by carefully adjusting the sintering stage. Previous investigations have established a sintering cycle for pure nickel consisting of 1325 ∘C for 12 h within an N2-5%H2 atmosphere. Nevertheless, microstructural, mechanical and magnetoelastic responses can still be greatly enhanced. In this context, the effects of hot isostatic pressing (HIP), and sintering atmosphere have been investigated. The application of an adequate HIP treatment leads to significant improvements in comparison to the reference sintering process. It achieves almost complete densification while increasing field-dependent elastic modulus from 8.1% up to 9.6%. Additionally, the sintering atmosphere has been proven to be a key factor in reducing impurities and hence facilitating magnetic domain motion. Three different atmospheres have been studied: N2-5%H2 (with a higher gas flow), N2-10%H2-0.1%CH4 and low vacuum. Minimum carbon contents have been registered using more reducing atmospheres (N2-5%H2 and N2-10%H2-0.1%CH4) which has led to values of field-dependent elastic modulus higher than 10%. This value is 2.5 times higher than that obtained when nickel parts are processed via conventional techniques. Moreover, although minimizing carbon content has been shown to be easier and more beneficial than achieving complete densification, both strategies could be used in combination to improve and maximize magnetoelastic performance.

Enhanced giant magneto-impedance effects in sandwich FINEMET/rGO/FeCo composite ribbons

This paper designed and regulated a unique sandwich FINEMET/rGO/FeCo composite ribbons (/F/GFC) with giant magneto-impedance (GMI) effect. The reduced graphene oxide (rGO) was synthesized on the FINEMET ribbons by one-step electroless plating, and FeCo layer was obtained by magnetron sputtering method. The study on morphology, structure, GMI effect and magnetic properties of /F/GFC illustrated that the currents passed through the highly conductive layer of rGO at high frequency, which greatly reducing the skin effect. In addition, the FeCo layer increased the permeability and provided a closed magnetic circuit, which can finally gain a large GMI effect at low frequency. The /F/GFC owned enhanced GMI effect, with the maximum GMI ratio reaching 70.32%, which was 2.1 times of the bare FINEMET ribbon, 1.4 times of the FINEMET/rGO composite ribbon and 1.2 times of the FINEMET/FeCo composite ribbon, respectively. The result can be explained by the regulating effect of magnetic dipole interaction on the magnetic properties of soft magnetic materials.

Dielectric, magnetic and humidity properties of Mg–Zn–Cr ferrites

Abstract In this study, Cr3+ substituted Mg0.75Zn0.25CrxFe2-xO4 (x = 0, 0.1, 0.3) (Mg–Zn–Cr) ferrites have been synthesized using chemical co-precipitation method. The crystal structure and phase formation of Mg–Zn–Cr ferrites have been analyzed by X-Ray diffraction (XRD) method. The crystal size (from 15.37 nm to 10.84 nm) and lattice constant (from 8.405 A to 8.384 A) of the crystallized in cubic crystal structure Mg–Zn–Cr samples decreased with Cr3+ contribution. The change in lattice strain determined by Williamson-Hall (W–H) graphs. Morphological and elemental analysis were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. The variations in temperature-dependent dielectric properties of samples between 290 K and 700 K were examined in the range from 20 Hz to 10 MHz. Curie temperature, where maximum dielectric constant is observed, shifted low temperatures with increasing Cr3+ contribution. This peak shift indicates that the materials have a relaxor ferroelectric character in accordance with the literature. Impedance analysis of Mg–Zn–Cr ferrites were investigated using Nyquist curves and relaxation process confirms Cole-Cole model. The magnetic properties of the samples in the range of ±5 kOe at 300 K were examined with the help of the Vibrating Sample Magnetometer (VSM). The M − H hysteresis loops of all samples showed the characteristic properties of soft magnetic materials. Finally, the effect of relative humidity (%RH) on the impedance of samples for different frequency values was investigated.

Identification and analysis of static and dynamic magnetization behavior sensitive to surface laser treatments within the electromagnetic field diffusion inside GO SiFe electrical steels

Surface laser treatment of soft magnetic materials, such as GO SiFe electrical steels, is mainly used to reduce iron losses by modifying the static and the dynamic magnetic properties. Laser treatment effect on mesoscopic electromagnetic properties of soft magnetic materials is presented. An experimental procedure using the Single Sheet Tester is performed on a magnetized sheet with specific exciting induction level and frequency. Transient average magnetic flux density through the sample cross-section and its corresponding applied magnetic field are measured. Data are identified in the time-domain with numerical results obtained by solving the diffusion equation using a 1-D discretization approach. The identification strategy requires a material law that includes both non-linear static and dynamic properties and describes the magnetic behavior due to domains and walls dynamics. Next, parametric and physical studies are performed on materials submitted to different laser treatments in order to determine and interpret their effects on the identified magnetic properties and the time response in the sheet’s depth. The results show that the static and the dynamic properties can be simultaneously improved. This analysis help to understand the impact of laser treatments on the static and the dynamic behaviour in order to improve the material magnetic performances within magnetic circuits inside electrical machines and transformers.

Incorporating the Soft Magnetic Material Degradation to Numerical Simulations

This article focuses on the numerical implementation of a continuous model for local degradation in soft magnetic materials. Cutting and punching processes required for producing electric machines impact the magnetic properties of soft magnetic materials. A simplified but effective model for considering local degradation of soft magnetic materials is defined and experimentally validated. The proposed model is then implemented in the source code of numerical simulation tool to assign directly at the mesh level the material characteristics as a function of the distance from the cut edge. The procedure as well as the flow chart for the implementation is described in detail. The proposed method allows avoiding the drawbacks of multilayer approaches and consequently increased model complexity and a required finer mesh density. A comparison between simulation results and measurements of lamination rings is presented and discussed.

Characterization and Modeling of Soft Magnetic Materials for Improved Estimation of PWM-Induced Iron Loss

This article investigates the iron loss properties of soft magnetic materials under conditions of high excitation frequency and varying premagnetized dc-bias fields (i.e., different magnetization states). Using measured iron loss data collected from the customized test equipment, a modified dynamic Jiles–Atherton model has been developed specifically for the purpose of achieving improved pulsewidth modulation (PWM)-induced iron loss estimation. The accuracy and scalability of the proposed prediction model for different conditions are evaluated including the flux ripple amplitude, excitation frequency, dc-bias field, and symmetry of the triangular waveform. Experimental results have confirmed that the proposed model can accurately predict the dynamic hysteresis loop and corresponding iron loss over a wide range of operating conditions. By introducing a companion iron loss model developed for fundamental and low-order harmonic fields, the total iron loss under inverter PWM voltage excitation is explored. The results show that model parameters derived from a limited number of tests can be used to predict the iron loss in a much broader operating range, which makes it a promising tool for PWM-induced iron loss estimation in new machine designs intended for demanding operating conditions.

Optimization of grain gene based on texture hereditary behavior of magnetic materials

Since the intrinsic properties of materials are determined by the properties and arrangement of atoms, including crystal structure and defects, there is a strong analogy between material genes and biological genes. Therefore, improving the performance of materials by optimizing their genes is a new idea of material upgrading. The <001> orientation texture is closely related to the magnetic properties of soft magnetic materials. We designed and experimentally demonstrated a gene optimization in an important soft magnetic material by electric current. The reduction of grain boundary hopping energy barrier caused by the distribution of electromagnetic field promoted <001> orientation grain nucleation and growth, which directly improved the initial <001> orientation grain gene, and the inheritance of <001> orientation texture was used to control the formation of recrystallization texture. Therefore, it is possible to utilize the gene optimization technique in many materials upgrading such as metal materials and biological materials according to the differences in electromagnetic properties of microstructures.

State-of-the-art and future trends in soft magnetic materials characterization with focus on electric machine design – Part 2

AbstractThe first part of this two-part article is about a retrospective view of material characterization, starting with the work of J. Epstein around the year 1900 and respective basic explanations. Consequently, the work presented herein is about the current state-of-the-art, recent developments, and future trends in characterization of ferromagnetic materials. Modeling is in fact a type of characterization, in a phenomenological and mathematical sense, and therefore it is treated with due attention in this article. Quantifying the properties of soft magnetic materials retains significant scientific attention. Thanks to new optimization techniques and advances in numerical evaluation, modern electromagnetic devices feature high utilization. Classical models exhibit assumptions that do not allow modern machine or device characterization with high accuracy. In this manuscript, typically applied techniques and recent incremental improvements, as well as newly developed models are introduced and discussed. Moreover, the significant impact of manufacturing on the materials’ characteristics and its quantification is illustrated. Within this article, a broad overview of the state-of-the-art as well as recent advances and future trends in soft magnetic material characterization is presented. Thus, it is a valuable reading for beginners and experts, from academia and industry alike.