Soft Magnetic Amorphous Alloys Research Articles

Exploring Microstructure and Magnetic Domain Evolution in the As-cast Soft Magnetic Fe74B20Nb2Hf2Si2 Alloy: A Comprehensive Study Using STEM, Lorentz TEM, and LM-STEM DPC Microscopy

This study delves into subtle changes in the microstructure and domain arrangement of a Fe74B20Nb2Hf2Si2 soft magnetic amorphous alloy. Utilizing transmission electron microscopy in Lorentz mode, low-magnification STEM, and differential phase contrast analysis (DPC), the research explores both the as-cast state and annealed samples. The results confirmed the formation of α-Fe, Fe23B6, Fe2(Hf, Nb), and Fe2B crystalline phases with increasing annealing temperature. Consequently, these crystallization stages induce significant alterations in magnetic domain size and spatial distribution due to microstructural changes. As the crystallization temperature rises, the volume fraction of crystalline phases increases, leading to modifications in the arrangement and size of magnetic domains. The decrease in magnetic domain size, associated with the formation of pinning sites during heat treatment, leads to alterations in soft magnetic properties. This includes an increase in coercivity (Hc) up to 40 A/m in the sample annealed at the temperature range of the third crystallization stage compared to the as-cast sample (1.5 A/m). Furthermore, as the annealing temperature rises, there is a corresponding increase in saturation magnetization (Ms), which reached to 1.71 T in the sample annealed within the temperature range of the third crystallization stage. These findings hold substantial implications for the practical applications of the Fe-based soft bulk metallic glasses (BMGs) alloy across various industries.

The Effects of Si Substitution with C on the Amorphous Forming Ability, Thermal Stability, and Magnetic Properties of an FeSiBPC Amorphous Alloy

The industrialization of Fe-based amorphous alloys with high a saturation magnetic flux density (Bs) has been limited so far due to their inadequate amorphous forming ability (AFA). In this study, the effects of substituting Si with C on the AFA, thermal stability, and magnetic properties of Fe82Si6−xB9P3Cx (x = 0–6) alloys were systematically investigated. The experimental results demonstrate that the AFA, thermal stability, and soft magnetic properties can be significantly enhanced by the addition of C. Specifically, at a copper wheel velocity of 40 m/s, the Fe82Si6−xB9P3Cx (x = 2, 3, 4, 5 and 6) alloy ribbons exhibit a fully amorphous structure in the as-spun state. The activation energy required for the α-Fe phase crystallization process in Fe82Si6−xB9P3Cx (x = 0, 2, 4, and 6) alloys is determined to be 326.74, 390.69, 441.06, and 183.87 kJ/mol, respectively. Among all of the compositions studied, the Fe82Si4B9P3C2 alloy exhibits optimized soft magnetic properties, including a low coercivity (Hc) of 1.7 A/m, a high effective permeability (μe) of 10608 (f = 1 kHz), and a relatively high Bs of 1.61 T. These improvements may be attributed to a more homogeneous and optimized magnetic domain structure being achieved through proper C addition. This work holds significant implications for the advancement of Fe-based soft magnetic amorphous alloys with high Bs.

Influence of Annealing Process on Soft Magnetic Properties of Fe-B-C-Si-P Amorphous Alloys.

It is well known that the annealing process plays a key role in tuning the properties of Fe-based amorphous soft magnetic alloys. However, the optimal annealing process for a particular amorphous alloy is often difficult to determine. Here, Fe81.4B13.2C2.8Si1.8P0.8 and Fe82.2B12.4C2.8Si1.8P0.8 amorphous alloys (denoted as Fe81.4 and Fe82.2) were prepared to systematically study the effects of the annealing temperature and time on the soft magnetic properties. The results show that the optimum annealing temperature ranges of the Fe81.4 and Fe82.2 amorphous alloys were 623 K to 653 K and 593 K to 623 K, and their coercivity (Hc) values were only 2.0-2.5 A/m and 1.3-2.7 A/m, respectively. Furthermore, a characteristic temperature Tai was obtained to guide the choosing of the annealing temperature at which the dBs/dT begins to decrease rapidly. Based on the theory of spontaneous magnetization, the relationship between Tai and the optimum annealing temperature ranges was analyzed. When the annealing temperature was higher than Tai, the effect of the internal magnetic field generated by spontaneous magnetization on the relaxation behavior was significantly reduced, and the alloys exhibited excellent soft magnetic properties. It is worth indicating that when annealed at 603 K (slightly higher than Tai), the Fe82.2 amorphous alloys exhibited excellent and stable soft magnetic properties even if annealed for a long time. The Hc of Fe82.2B12.4C2.8Si1.8P0.8 amorphous alloys was only 1.9 A/m when annealed at 603 K for 330 min. This value of Tai is expected to provide a suggestion for the proper annealing temperature of other amorphous soft magnetic alloys.

Revealing the role of Co element on local structure and magnetism in Fe-Si-B-C amorphous alloys through calculations and experiments

In order to understand the role of Co element on glass-forming ability(GFA) and magnetization of Fe-Si-B-C amorphous alloys, we analyse atomic structures, electronic structure and magnetic moments by ab initio molecular dynamics simulations.The GFA and magnetization of (Fe0.8Co0.2)83.6Si1B15C0.4 amorphous alloy are best in our experiment and simulation. According to calculations of the local structures, electronic structures, and magnetic moments,Fe-centered or Co-centered deformed body-centered cubic units and B-centered prism units predominate in the local structures of Fe-Co-Si-B-C amorphous alloys. In particular, the ratio of Co to Fe of 1:4 in (Fe0.8Co0.2)83.6Si1B15C0.4 amorphous alloy is the critical factor for enhancing GFA and magnetization, which improves the degree of atomic chaos, the stability of the local atomic structures and enhances magnetic moments. However, the excessive addition of Co leads glass-forming ability and magnetization to reduce.This work offers insight into the relationship between local atomic structures and Fe-Co-based amorphous alloy magnetization and offers suggestions for the development of high-performing soft-magnetic amorphous alloys.

Flexible Mini‐Inductors with Ultra‐High Inductance Density Directly Cut from Soft Magnetic Amorphous Alloys by Femtosecond Laser

AbstractInductors are indispensable parts in power modules of electronic devices. With the rapid development of flexible and wearable electronic devices, developing flexible micro‐inductors with large energy storage has become an urgent task. In this research, a sophisticated femtosecond laser ablation technique is employed to craft circular spiral mini‐inductors via selective etching of soft magnetic amorphous alloy ribbons. Remarkably, while these inductors possess dimensions akin to human fingerprints, they demonstrate an impressively elevated inductance value of ≈1.15 µH at 1 MHz. The inductance density is ≈280–390 nH mm−2, which is ≈10 times larger than conventional circular spiral inductors and is attributed to the high permeability of the amorphous alloys. Furthermore, the inductors showcase commendable flexibility, marked by stellar elasticity and a bending endurance exceeding 2500 cycles, thanks to the amorphous alloys' superior elastic strain limit. When integrated with an LM2576‐3.3BT buck converter, the fabricated inductor achieved a peak power conversion efficiency nearing 70%. These findings underscore the potential of such flexible mini‐inductors in the landscape of flexible electronics.

Magnetic properties of the amorphous Co-Fe-Cr-Si-B alloy after annealing in unsaturated magnetic field

The regularities of influence of temperature and intensity of a longitudinal magnetic field significantly less than the saturation field during annealing on the magnetic properties of an amorphous soft magnetic alloy based on Co have been studied. The possibility of the effectiveness of such treatment in comparison with traditional annealing without a field due to partial or complete suppression of stabilization of domain boundaries because of directional ordering is demonstrated. Annealing at temperatures below the Curie point with the application of unsaturated field exceeding the saturation field of the residual induction of an amorphous alloy in as-quenched state (40 A/m) showed the greatest efficiency compared with annealing without a field in terms of simultaneously reducing the coercive force Hc and increasing the low-field permeability µ0.3 and maximum permeability µmax. In comparison with non-field annealing, depending on the conditions of unsaturated magnetic field annealing, the possibility of reducing Hc by 39 %, increasing µmax by 4.5 times and µ0.3 by 3.8 times is shown. After annealing in unsaturated field on the magnetization curve of the alloy Co69Fe3.7Cr3.8Si12.5B11, the perminvar region, as well as the parabolic region where Rayleigh's law is fulfilled, end in lower fields than after annealing without a field. The results obtained are discussed taking into account the occurrence of various physical processes in the alloy during heat treatment.

Clean production of Fe-based amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore and apatite

Clean production of Fe-based amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore and apatite

AIMD study and experimental verification of Ge-doped Fe80P13C7 amorphous soft magnetic alloys

Fe80P13-xC7Gex (x = 0, 2, 4) amorphous alloys were synthesized by rapid solidification technique and studied using Ab-initio molecular dynamics (AIMD) and first-principles calculations based on density-functional theory (DFT) for their electronic structures. Brillouin function was used to calculate saturation magnetization (µ0MS) at elevated temperatures utilizing experimentally measured Curie temperature (TC) and µ0MS at 0 K calculated by DFT.To verify the calculated µ0MS, ingots of Fe80P13-xC7Gex (x = 0, 1, 2, 3, 4, 5, 6) alloy were prepared by melt-spinning. An increase in experimental µ0MS with Ge concentration agrees with the calculated µ0MS. TC also increases with Ge concentration. Partial substitution of Ge for P enhances the µ0MS to 1.63 T (x = 4) from 1.46 T (x = 0), which indicated that the Fe80P13-xC7Gex (x = 4) shows optimum soft magnetic properties.

Plasticity and brittleness of Fe-based amorphous alloy strips assessed via a single abrasive impact method

Fe-based soft magnetic amorphous alloys represent the next generation of magnetic core materials and are expected to replace silicon steel sheets in many applications. An economical and fast methodology for the study of the plasticity and brittleness of this material is however necessary to permit its widespread use. Abrasive water jetting is a cold processing technique that has great potential for use in the fabrication and inspection of Fe-based amorphous alloy parts. However, research on this technique is currently lacking. In order to assess the plasticity and brittleness of Fe-based amorphous alloys by considering abrasive impacts, this work investigates the effect of impact speed and impact angle on the removal process in Fe-based amorphous alloys and establishes the corresponding abrasive erosion mechanism. It is found that Fe-based amorphous alloys exhibit four primary responses: shear slip, viscous flow, shear crack formation, and brittle fracture; the plasticity and brittleness of Fe-based amorphous alloys are assessed by considering the impact morphology and mechanism.

COMPARISON OF MODELS OF MAGNETIZATION CURVES AND HYSTERESIS LOOPS ACCORDING TO THE GILES-ATHERTON MODEL FOR SOFT MAGNETIC AMORPHOUS ALLOYS

The subject of research in the article is ferromagnetic soft magnetic amorphous materials and alloys, which are used in power sources of automated control systems, and in vehicle electrical installations. The aim of the work is an objective comparison of two magnetization models for soft magnetic amorphous alloys - the main magnetization curve using approximation functions and the Giles-Atherton hysteresis loop model. In the study, the least squares method was used to optimize the main magnetization curve and the Giles-Atherton hysteresis loop optimization method with the aim of its maximum coincidence with the experimentally obtained loop. Experimental and reference data for common types of magnetically soft amorphous alloys were used for modeling. As a criterion of model accuracy for both modeling methods, the relative error in determining the magnetic induction value was chosen, and the experimental value obtained from the real hysteresis loop of a magnetically soft amorphous alloy was taken as its exact value, and the approximate value was taken from calculations of the magnetic induction value using the methods of approximating the magnetization curve and simulation of the hysteresis loop using the Giles-Atherton method. As a result of the research, it was revealed that both models of magnetization of magnetically soft amorphous materials give simulation results similar in accuracy. The obtained results of the study can be used to select an appropriate magnetization model for the mathematical description of ferromagnetic devices using magnetically soft amorphous metals and alloys. The final conclusion about the advantages of a particular model can only be made on the basis of the ultimate goals of the analysis.

Core-shell structure and stability of nanocrystalline precipitates in Fe83.3Si4B8P4Cu0.7 soft magnetic amorphous alloy

The core-shell nanostructure of α-Fe precipitates was investigated in a recently developed high-performance Fe83.3Si4B8P4Cu0.7 nanocrystalline soft magnetic alloy utilizing small-angle neutron scattering (SANS) and atom probe tomography (APT). SANS measurements under a saturating magnetic field provided evidence of core-shell structures at the nanoscale. Moreover, the core-shell structure was directly visualized from APT analysis, where P-enriched shells were found around Fe-enriched cores due to the large negative heat of mixing between Fe and P elements and the slow diffusion of P atoms. The core-shell nanostructures induced by nanoscale partitioning are effective in stabilizing the residual amorphous matrix and suppressing the crystal growth. Our findings provide insight into the microstructure of Fe-based amorphous alloys and have direct implications in alloy design for the improvement of the soft magnetic properties.

Effect of W Addition on Fe-P-C-B Soft-Magnetic Amorphous Alloy

In this work, the thermal behavior, soft magnetic properties, and structure of Fe86-xP11C2B1Wx (x = 0, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, and 4) amorphous alloys were researched by several experimental methods and ab initio molecular dynamics. The addition of W improved the thermal stability of the alloy system when the first onset crystallization temperature (Tx1) increased from 655 K to 711 K, significantly reduced the coercivity Hc, and decreased the saturation magnetization Bs. The Fe85.6P11C2B1W0.4 alloy showed optimal soft magnetic performance, with low Hc of 1.4 A/m and relatively good Bs of 1.52 T. The simulation results suggested that W atoms increased the distance of the neighboring Fe-Fe pair, reduced the coordination number, narrowed the gap between the spin-up and spin-down electrons of each atom, and decreased the average magnetic moment of the Fe atoms. This work demonstrates a micro-alloying strategy to greatly reduce Hc while maintaining high Bs.

Effect of melt thermal history on magnetic properties and thermal stability in Fe–Si–B–C amorphous alloy

Melt thermal history is highly heritable to the structure of metallic glass frozen by rapid quenching liquid. In this paper, the influences of melt thermal history above liquidus temperature on magnetic properties and thermal stability have been systematically investigated in Fe75Si9B12C4 amorphous alloy. The results show that both magnetic properties and thermal stability of the alloy show a non-overlapping feature for the alloys undergone melt heat preservation during heating and cooling process, respectively. It was found that melt thermal history can significantly affect the structural change of the alloy, and thus results in hysteresis behaviors of magnetic properties and thermal stability through changing degree of amorphization. These findings could help understand the melt thermal history and design preparation technology of soft magnetic amorphous alloys.

Excellent magnetic softness-magnetization synergy and suppressed defect activation in soft magnetic amorphous alloys by magnetic field annealing

Fe-based amorphous alloys with high saturation magnetic flux density (Bs) are increasingly attractive from both scientific and technological points of view, however, they usually suffer from the trade-off between magnetization and softness. In this work, we explore the soft magnetic properties (SMPs), magnetic and atomic structures, and defect activation during creep deformation of as-quenched and annealed Fe82.65-xCoxSi2B14Cu1.35 (x = 0–20) amorphous alloys (AAs). Improved magnetic softness-magnetization synergy has been realized in all these alloys by field annealing. Particularly, superb SMPs with super-high Bs of 1.86 T, low coercivity of 1.2 A/m and high effective permeability of 16300 are obtained in the Fe66.65Co16Si2B14Cu1.35 AA. The locally regularized arrangement of domains, homogenized structure with less structural/magnetic defects and suppressed crystal-like ordering by field annealing contribute synergistically to the superb SMPs. Besides, the relaxation time spectra obtained from creep deformation indicate less liquid-like and solid-like defects activated in the field-annealed AA, which is correlated with the structural homogenization and superb SMPs. This work provides new and comprehensive insight into the interplay among external field, heterogeneous structure, SMPs and defect activation of Fe-based AAs, and offers a promising pathway for softening amorphous alloys with high Bs.

Radio‐Frequency Rapid Thermal Processing Enabling Spatial Phase Transformation and Nanocrystallization of Soft Magnetic Amorphous Alloys

Thermal processing of soft magnetic amorphous and nanocrystalline alloys is explored under the influence of radio‐frequency induction‐heating techniques. Direct induction‐heating concepts based on longitudinal and transverse flux heating are examined and the details of electromagnetic fields interaction with metallic strips are discussed by analytical calculations as well as finite element analysis. Initial experimental results confirming spatial control of phase transformations and nanocrystallization within a single strip of Finemet Fe‐based amorphous ribbons are reported. The degree to which primary and secondary crystallization temperature are achieved depends on the spacing between the ribbon relative to the induction coil as well as the coil design and configuration. For transverse coil configurations, the local temperature and therefore microstructural evolution is different across the lateral dimension of processed ribbons, with reduced gap sizes producing enhanced peak temperatures and larger temperature distributions with greater spatial variation in microstructure. In addition, indirect susceptor‐based induction heating under tension is performed and the impact of microstructure is demonstrated. Herein, potential for exploiting spatially optimized phase transformations is illustrated through electromagnetic field–assisted processing in a scalable manufacturing process with amorphous and nanocrystalline soft magnetic alloys.

Theoretical Prediction and Experimental Validation of the Glass-Forming Ability and Magnetic Properties of Fe-Si-B Metallic Glasses from Atomic Structures.

Developing new soft magnetic amorphous alloys with a low cost and high saturation magnetization (Bs) in a simple alloy system has attracted substantial attention for industrialization and commercialization. Herein, the glass-forming ability (GFA), thermodynamic properties, soft magnetic properties, and atomic structures of Fe80+xSi5−xB15 (x = 0–4) amorphous soft magnetic alloys were investigated by ab initio molecular dynamics (AIMD) simulations and experiments. The pair distribution function (PDF), Voronoi polyhedron (VP), coordination number (CN), and chemical short- range order (CSRO) were analyzed based on the AIMD simulations for elucidating the correlations between the atomic structures with the glass-forming ability and magnetic properties. For the studied compositions, the Fe82Si3B15 amorphous alloy was found to exhibit the strongest solute–solute avoidance effect, the longest Fe-Fe bond, a relatively high partial CN for the Fe-Fe pair, and the most pronounced tendency to form more stable clusters. The simulation results indicated that Fe82Si3B15 was the optimum composition balancing the saturation magnetization and the GFA. This prediction was confirmed by experimental observations. The presented work provides a reference for synthesizing new Fe-Si-B magnetic amorphous alloys.

Effect of continuous rapid annealing on the microstructure and properties of Fe85P11C2B2 amorphous alloy

Fe-based amorphous alloys are promising soft magnetic materials for applications in power electronic devices. However, the practical use is inevitably limited by their brittleness that results from annealing. In this paper, an Fe85P11C2B2 amorphous alloy was heat treated by using a self-designed continuous rapid annealing equipment. After rapidly annealing the amorphous precursors at 773 K for 0.3 s, the α-Fe phase with a size of 2 ∼ 5 nm precipitated, and the ribbon sample exhibits a high saturation magnetization (Bs) of 1.66 T and low coercivity (Hc) of 7.6 A/m in combination with good bending ductility. This work will provide a new heat treatment method for the soft-magnetic Fe-based amorphous alloy that can inhibit annealing-induced brittleness.

Physical Modification of Products Made of Soft Magnetic Materials under Texturing Effects

The results of improving physical properties of different types of magnetic cores made of soft magnetic crystalline and amorphous alloys based on siliceous iron are presented. Methods and modes of controlling orientational, dimensional and dynamic parameters of magnetic domains by means of a uniaxially textured complex of thermomagnetic, locally laser, and plane deformation effects have been developed. As a result, in electrical magnetic cores made of anisotropic iron-silicon steels of 3407, 3408 grades a decrease in eddy-current magnetic losses by 25–35% and an increase in magnetic permeability by 1.5–2 times have been achieved.

Effect of Substituting Hf for Zr on Fe-Co-M-Nb-B (M = Zr, Hf) Amorphous Alloys with High Saturation Magnetization

The soft magnetic amorphous ribbons of (FexCo1−x)85M9Nb1B5 (M = Zr or Hf, x = 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9) were investigated in this study. Replacing Zr by Hf turned out to increase saturation magnetization and, at the same time, reduce the coercivity, both of which serve together in enhancing the soft magnetic performance of the alloys. Moreover, the optimum ratio of Fe/Co was determined after the survey on different alloys with varying Fe/Co ratio resulting in the maximum saturation magnetization while keeping the coercivity low. After optimization, the highest saturation magnetization of 1.62 T was achieved with coercivity of 11 A/m. While substitution of Hf for Zr slightly reduced the crystallization onset temperature of the amorphous structure, the thermal stability of the soft magnetic amorphous alloys was not significantly affected by the Zr/Hf replacement.

Micromechanical Force Sensor Using the Stress-Impedance Effect of Soft Magnetic FeCuNbSiB.

By using the stress–impedance (SI) effect of a soft magnetic amorphous FeCuNbSiB alloy, a micromachined force sensor was fabricated and characterized. The alloy was used as a sputtered thin film of 500 nm thickness. To clarify the SI effect in the used material as a thin film, its magnetic and mechanical properties were first investigated. The stress dependence of the magnetic permeability was shown to be caused by the used transducer effect. The sputtered thin film also exhibited a large yield strength of 983 GPa. Even though the fabrication technology for the device is very simple, characterization revealed a gauge factor (GF) of 756, which is several times larger than that achieved with conventional transducer effects, such as the piezoresistive effect. The fabricated device shows great application potential as a tactile sensor.