Soft Magnetic Amorphous Alloys Research Articles

Development of soft magnetic amorphous alloys with distinctly high Fe content

This paper reports on the preparation of Fe82.7-85.7Si2-4.9B9.2-11.2P1.5-2.7C0.8 soft magnetic amorphous alloys with a distinctly high Fe content of 93.5-95.5 wt.% by component design and composition adjustment. All alloys can be readily fabricated into completely amorphous ribbon samples with good surface quality by the single copper roller melt-spinning method. These alloys show good bending ductility and excellent magnetic properties after annealing, i.e., low coercivity ( H c) of 3.3-5.9 A/m, high permeability ( μ e) of 5000-10000 and high flux saturation density ( B s) of 1.63-1.66 T. The mechanism of the good glass forming ability (GFA) and soft-magnetic properties are explored. The amorphous alloys with the high Fe content comparable to that of the desired high Si alloy can be promising candidates for the potential application in electric devices.

Preparation and properties of Fe[sbnd]B[sbnd]P[sbnd]Sn soft magnetic amorphous alloys with Fe contents higher than 83%

The composition design for the Fe-based amorphous alloys with high Fe contents is introduced based on the Nearly-Free-Electron model, which indicates that there is a favorable electron concentration (e/a) value for amorphous formation. The FeBPSn amorphous alloys with Fe contents higher than 83% have been prepared based on the favorable (e/a) value. The influences of Sn on the amorphous forming ability (AFA) and magnetic properties are investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and vibrating sample magnetometer (VSM), respectively. The results show that the inflexion of the coercive force Hc~(e/a) relationship is just contrary to that of the AFA~(e/a) relationship. The present work provides a convenient way to design Fe-based amorphous alloys with good magnetic performances by the metalloid admixture according to the favorable (e/a) value.

Influence of heat treatment on the efficiency of impact fragmentation of amorphous alloy Fe73.5Cu1Nb3Si13.5B9 ribbons

The mechanism of impact fracture of soft magnetic amorphous alloy Fe73.5Cu1Nb3Si13.5B9 ribbons in a disintegrator after heat treatment at a temperature from the range 300–700°C and the fractional composition of the formed powder are studied. The temperature ranges of a change in the mechanism of ribbon fracture are determined. The particle size distribution is shown to change weakly within the revealed temperature ranges.

Excellent soft magnetic Fe-Co-B-based amorphous alloys with extremely high saturation magnetization above 1.85 T and low coercivity below 3 A/m

Abstract Extremely good soft magnetic properties of high saturation magnetization ( B s ) above 1.8 T and low coercivity ( H c ) below 5 A/m were obtained for (Fe 1- x Co x ) 83 B 16 Si 1 ( x = 0.1–0.3) amorphous ribbons annealed at the temperature between T x1 -120 K and T x1 -40 K. Here T x1 is the onset temperature of the first exothermic crystallization peak. The best characteristics were 1.86 T for B s and 3 A/m for H c at x = 0.2. There are no previous data on the melt-spun alloys with high B s above 1.8 T and low H c below 5 A/m and hence the present amorphous alloys are regarded as a novel good soft magnetic alloy with high B s comparable to Fe-Si steels. Curie temperature ( T c ) of the x = 0.2 alloy was above T x1 (708 K), implying high thermal stability of magnetic characteristics. The saturated magnetostriction for x = 0.2 was about 32 ppm and the effective permeability at 1 kHz showed as high as 1.6 × 10 4 . The high B s can be attributed to the low metalloid content containing mainly B element which suppresses effectively the reductions of B s and T c among metalloid elements, as well as the optimum Co/Fe content ratio with the maximum magnetic interaction in conjunction with maximum atomic volume. Moreover, these alloy ribbons exhibited good bending ductility even after optimum annealing treatment, in addition to high Vickers hardness of about 1000 and improved corrosion resistance comparing with the corresponding Co-free alloy. The excellent soft magnetic amorphous alloys are promising for further extension as engineering soft magnetic materials.

Large adiabatic temperature rise above the water ice point of a minor Fe substituted Gd50Co50 amorphous alloy

In this study, we have successfully improved the Curie temperature of Gd50Co50 amorphous alloy from 267K to 277K by a minor Fe addition as a replacement for Co. The Gd50Co48Fe2 as-spun ribbons exhibit typical characteristics of a soft magnetic amorphous alloy. The magnetic entropy change peak for this amorphous alloy was slightly decreased by the minor Fe addition, but the adiabatic temperature rise (ΔTad) of the Gd50Co48Fe2 amorphous alloy is comparable to that of the Gd50Co50 amorphous alloy, both of which are larger than those of other metallic glasses near the ice point of water. The maximum ΔTad of the Gd50Co48Fe2 amorphous ribbon at 277.5K is about 1.44K under 1T, 2.44K under 2T, 3.31K under 3T, 4.1K under 4T and about 4.84K under 5T. The large maximum value of ΔTad above the ice point indicates that the Gd50Co48Fe2 amorphous alloy could be an ideal candidate for the high efficient magnetic refrigerant in a household refrigerator.

Magnetization distribution in a soft magnetic amorphous alloy ribbon in as-quenched state and efficiency of heat treatment

The effect of heat treatment in air on the formation of magnetic properties has been studied based on the example of soft magnetic Fe77Ni1Si9B13 and Fe81B13Si4C2 amorphous ribbons characterized by positive magneto-striction. The magnetization distribution in the ribbons in the as-quenched state was shown to affect the efficiency of annealing. Under certain conditions, heat treatment, which results in the formation of mainly amorphous state of ribbon surface, is more efficient for samples characterized by high volume of orthogonally magnetized domains. This can be related to high in-plane tensile stresses, which are induced by hydrogen and oxygen atoms introduced into the ribbon surface upon its interaction with atmospheric water vapor.

Investigation on the crystallization mechanism difference between FINEMET® and NANOMET® type Fe-based soft magnetic amorphous alloys

In this article, the atomic behaviors of Nb and P in Fe-based amorphous alloys during nano-crystallization process were studied by the combination of ab initio molecular dynamics simulations and experimental measurements. The inclusion of Nb is found to be tightly bonded with B, resulting in the formation of diffusion barrier that could prevent the over-growth of α-(Fe, Si) grains and the promotion of larger amount of α-(Fe, Si) participation. The P inclusion could delay the diffusion of the metalloids that have to be expelled from the α-(Fe, Si) crystallization region so that the grain growth could be reduced with fast but practically achievable heating rates. The combined addition of P and Nb in high Fe content amorphous alloys failed in exhibiting the potential of good magnetic softness with slow heating (10 K/min) annealing at various temperatures. The sample with optimum crystallization process with confined grain size was annealed at 653 K, with the grain size of 31 nm and a coercivity of ∼120 A/m, much too large to meet the application requirements and to be compared with the currently well-studied alloy systems. This attempt suggests that the inclusion of early transition metal elements might not be effective enough to suppress grain growth in crystallizing high Fe content amorphous alloys.

Effect of heat treatment in air and a chemically active environment on the magnetic properties of cobalt-based soft magnetic amorphous alloys

The influence of heat treatment in air on the level of magnetic properties has been studied on the example of a ribbon of an amorphous cobalt-based (Co–Fe–Ni–Cr–Si–B) soft-magnetic alloy with a nearzero saturation magnetostriction. The investigation of the interaction of the ribbon surface with water and water vapor and its influence on the magnetization distribution showed the possibility of applying surface treatment to determine the sign of saturation magnetostriction. The sign of saturation magnetostriction in the initial (quenched) state confirmed the presence of a negative magnetostriction in the ribbon. Based on the results obtained, the dependence of the sign of saturation magnetostriction on the structural state that is obtained upon heat treatment has been revealed.

New Fe-based soft magnetic amorphous alloys with high saturation magnetization and good corrosion resistance for dust core application

Fe-rich amorphous dust core alloys with minor-addition of Mo and/or Cr were synthesized because of the industrial request of mass production of high efficient low core loss Fe-based dust cores. It was found that the present Fe-(Cr, Mo)-P-B-Si-(C) amorphous alloy ribbons exhibit good soft magnetic properties of above 1.5 T for saturation magnetization, below 10 A/m for coercivity and rather good corrosion resistance in 3%NaCl aqueous solution. Besides, the amorphous alloy ribbons exhibit good bending ductility in as-spun and optimally annealed states. It is noticed that these characteristics are much superior to those for commercial Fe-Cr-Nb-P-B-Si soft magnetic dust core alloy (SENNTIX). In addition, the annealing treatment was noticed to cause the improvement of corrosion resistance without detriment to bending ductility. The new Fe-based soft magnetic alloys with good combined characteristics are expected to be used as the basic material as high-efficient soft magnetic dust cores in a high frequency range.

Production feature of soft magnetic amorphous alloys

Methods for making nanocrystalline alloys have been discussed. Temperature dependences of the surface tension (σ), electric resistivity (ρ), magnetic susceptibility (χ) and kinematic viscosity (ν) have been obtained. Comparison of the properties of amorphous ribbons obtained by the pilot and serial technologies has been conducted. Science-based technology of multi-component alloy smelting makes it possible to prepare equilibrium smelt, the structure of which has a significant effect on the properties of the amorphous ribbon before spinning and kinetics of its crystallization has been offered.

Mechanisms of the Magnetic Properties Improvement of Amorphous Soft Magnetic Fe- and Co-based Alloys as a Result of the in-air Heat Treatment

Physical causes of the formation of magnetic characteristics amorphous soft magnetic alloys under heat treatment in air have been studied. It has been established that the physical causes of the formation of the magnetic characteristics of the cobalt-based alloys are the same as those for iron-based alloys. Change in the magnetic characteristics after annealing results from the relaxation of the quenching induced internal stresses, as well as from the effect of the stresses induced by the hydrogen and oxygen atoms embedded into the ribbon surface in the course of its interaction with water vapor in air and by the formation of the amorphous-crystalline surface layer. The study of the magnetization distribution and the magnetic characteristics of the Co–Fe–Ni–Cr–Si–B amorphous soft magnetic alloy have shown the possibility of using the vapor treatment of the amorphous soft magnetic alloy ribbon surface to determine the sign of its magnetostriction. The magnetostriction sign dependence on the structural state of the ribbon is found on the basis of the obtained results.

A short-range ordering in soft magnetic Fe-based metallic glasses studied by Mössbauer spectroscopy and Reverse Monte Carlo method

Selected soft magnetic amorphous alloys Fe80B20, Fe70Nb10B20 and Fe62Nb8B30 were produced by the melt-spinning and characterized by X-ray diffraction (XRD), transmission Mössbauer spectroscopy (MS), Reverse Monte Carlo modeling (RMC) and relative magnetic permeability measurements. The Mössbauer spectroscopy allowed to study the local environments of the Fe-centered atoms in the amorphous structure of binary and ternary glassy alloys. The MS provided also information about the changes in the amorphous structure due to the modification of chemical composition by various boron and niobium content. The RMC simulation based on the structure factors determined by synchrotron XRD measurements was also used in modeling of the atomic arrangements and short-range order in Fe-based model alloys. Addition of boron and niobium in the ternary model alloys affected the disorder in as-cast state and also influenced on the number of nearest neighbor Fe–Fe atoms, consequently. The distributions of Fe- and B-centered coordination numbers showed that N=10, 9 and 8 are dominated around Fe atoms and N=9, 8 and 7 had the largest population around B atoms in the examined amorphous alloys. Moreover, the relationship between the content of the alloying elements, the local atomic ordering and the magnetic permeability (magnetic after-effects) was mentioned.

B23-P-04High glass forming ability Fe-based soft magnetic amorphous alloys

Amorphous alloys, or so called bulk metallic glass, are well known as a functional material with high strength, good wear and corrosion resistance, and excellent soft magnetic properties. Among all the compositions, Fe-based and Co-based amorphous alloys exhibit high maximum magnetic flux, high permeability, low loss, and low coercivity, are high grade soft magnetic materials. In addition, Fe-based soft magnetic amorphous alloys perform higher maximum magnetic flux and lower cost than Co-based alloys. However, the glass forming ability (GFA) of Fe-based soft magnetic amorphous alloys is a stumbling block to limit the critical size and the application field. In the previous research, increasing metalloid content is benefit for GFA but is tend to be harmful for the maximum magnetic flux and thus lower the performance. In this study, the goal is to increase the GFA of Fe-based soft magnetic amorphous alloys by trace element adding. Meanwhile, to maintain the excellent soft magnetic properties. The amorphous nature, morphologies of the porous metallic glasses, and mechanical properties are examined by X-ray diffraction (XRD), and scanning electron microscopy (SEM). In addition, the GFA of Fe-based alloys are analysis by differential scanning calorimetry (DSC). All of the results included magnetic properties will be discussed in details. B23-P-03 doi:10.1093/jmicro/dfv277

The Development of a Shield of Amorphous Soft Magnetic Alloy to Reduce the Effect of the Earth’s Magnetic Field on the Sensitive Element of a Photoelectronic Spectrometer

The results of calculations of the effi ciency of the shielding of a photoelectronic spectrometer by amorphous alloys, designed to protect the instrument from the Earth's magnetic fi eld, are presented. The distribution of the magnetic induction inside the shield for different positions of the instrument is measured. The anisotropy of the shielding properties of a magnetopolymer shield is investigated. An analysis of modern trends in investigating the effect of physical fi elds, in particular, the Earth's magnetic fi eld, on technical devices shows that most attention is being devoted to fi nding optimal methods of shielding (1-4). There are a number of instruments available at present, the readings of which are sensitive to the Earth's magnetic fi eld. These include instruments which use the physical laws of motion of charged particles in magnetic and electric fi elds: mass spectrometers, scanning electron microscopes, x-ray fl uorescent spectrometers, etc. Both static and variable magnetic fi elds of different fre- quency can defl ect particles from their normal trajectories of motion and thereby distort the readings of such instruments. Another form of magnetically sensitive devices is systems by means of which one can measure extremely small magnetic fi elds. For example, the magnetocardiograph, designed to carry out medical diagnostics, detects magnetic fi elds, the source of which is the heart. These fi elds are very weak, and hence it is important to eliminate the effect of induced external magnetic fi elds on the results of the measurements. An electromagnetic shield is a necessary part of the cabinet containing the magnetic tomography apparatus. If its integrity is disturbed or there is no shielding, extensive techniques cannot be correctly used, in view of the magnetic interference produced by surrounding electronic equipment and the geomagnetic fi eld. Standards in the area of the electromagnetic compatibility of technical instruments lay down the requirements for stability to electromagnetic interference, the quality of the electric power in the networks, and new methods of testing (5, 6). In practice, one cannot always transport the technical equipment a distance at which the fi eld is reduced to the thresh- old limit value. In this case, it is necessary to use shielding materials. The shielding of constant and low-frequency magnetic fi elds is the most complicated operation. For such purposes, one requires materials possessing high magnetic permeability and saturation induction, and low coercive force. They should remain capable of operating in diffi cult working conditions: they must be insensitive to mechanical and dynamic disturbances (deformations and vibrations), they must operate over a wide temperature range, and must have highly reproducible properties. To protect measuring instruments from the effect of extraneous physical fi elds, they are often placed in massive closed casings made of ferromagnetic material - usually permalloy. However, these shields have considerable drawbacks: the high shielding factor is not retained under mechanical actions, which inevitably arise during the manufacture and assembling the

Interaction of the surface of ribbons of amorphous soft-magnetic alloys with vapor during isothermal holding upon heat treatment

The effect of in-air heat treatment in combination with water vapor on the magnetization distribution and magnetic properties has been investigated based on the example of ribbons of amorphous soft-magnetic alloys Fe77Ni1Si9B13 and Fe81B13Si4C2 with positive magnetostriction. The results of the investigation showed the temperature lag of the dependence of the maximum magnetic permeability and of relative volume of domains with orthogonal magnetization on the isothermal-holding temperature. This effect can be associated with the inhibition of processes of surface crystallization by hydrogen and oxygen atoms introduced into the ribbon surface. Distinctive features of the heat treatment with and without vapor on the magnetization distribution in the ribbon plane that are explained within the theory of directed ordering with allowance for the processes of crystallization at the cooling stage have been found. This demonstrates the importance of the contribution of diffusion processes at this stage of treatment to the formation of the level of magnetic properties. It has been shown that the interaction of the ribbon surface with water vapor is not physical adsorption. Interaction with atmospheric gases is carried out by dispersion forces and exerts an influence on the magnetization distribution in the ribbon plane and maximum magnetic permeability.

Amorphous and Nanocomposite Materials for Energy-Efficient Electric Motors

Fil: Silveyra, Josefina Maria. University Of Carnegie Mellon; Estados Unidos. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica. Laboratorio de Solidos Amorfos; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay. Instituto de Tecnologias y Ciencias de la Ingenieria; Argentina; Argentina

The influence of P on glass forming ability and clusters in melt of FeSiBP amorphous soft-magnetic alloy

Our experiment focused on investigating the P content dependences of the ability to form glass, the soft-magnetic properties of, and the clusters in melting Fe85−xSi4B11Px (x = 1–6), amorphous soft-magnetic alloys. The experimental results demonstrate that the alloys with proper P content (3–6 at.%) are prone to form a completely amorphous structure with a larger glass-forming ability (GFA); hence, amorphous alloys prepared by industry-grade raw materials can be well produced in an air atmosphere. The melted alloy has higher stability and larger GFA when there is no dominant cluster or when multi-species clusters coexist. The Fe82Si4B11P3 amorphous alloy exhibited a high saturation magnetic flux density of up to 1.66 T, a low coercivity of about 2.2 A/m, and a high effective permeability of more than 1.2 × 104 at 1 kHz under a field of 1 A/m. The combination of excellent soft-magnetic properties, good productivity and low cost stability suggest that the FeSiBP alloys are promising soft-magnetic materials, particularly with applications in the electronic industry.

Magnetic Properties of Rapidly Quenched Ribbons of Soft Magnetic Iron-Based Alloys after Annealing in Air and in Vacuum

The physical reasons of influence of heat treatment in vacuum and air on magnetic properties of ribbon’s of amorphous soft magnetic iron-based alloys were investigated. It is shown that the heat treatment in the air contributes to retrieve the status of a material with lower specific magnetic losses. The reason for this is the formation during annealing of increased concentration along the axis of the ribbon of embedded in the surface atoms of hydrogen and oxygen. In this direction induced pseudo-uniaxial tensile stress, contributing to the reduction of the period of the domain structure and the speed of domain walls motion in the process of magnetization reversal.

Relaxation of bending stresses and the reversibility of residual stresses in amorphous soft magnetic alloys

The reversibility of residual bending stresses is revealed in ribbon samples of cobalt- and iron-based amorphous alloys Co69Fe3.7Cr3.8Si12.5B11 and Fe57Co31Si2.9B9.1: the ribbons that are free of applied stresses and bent under the action of residual stresses become completely or incompletely straight upon annealing at the initial temperatures. The influence of annealing on the relaxation of bending stresses is studied. Preliminary annealing is found to sharply decrease the relaxation rate of bending stresses, and the initial stage of fast relaxation of these stresses is absent. Complete straightening of preliminarily annealed ribbons is shown to occur at significantly higher temperatures than that of the initial ribbons. Incomplete straightening of the ribbons is explained by the fact that bending stresses relaxation at high annealing temperatures proceeds due to both reversible anelastic deformation and viscous flow, which is a fully irreversible process. Incomplete reversibility is also caused by irreversible processes, such as the release of excess free volume and clustering (detected by small-angle X-ray scattering). The revealed differences in the relaxation processes that occur in the cobalt- and iron-based amorphous alloys are discussed in terms of different atomic diffusion mobilities in these alloys.

High-Frequency Electric Properties of Amorphous Soft Magnetic Cobalt-Based Alloys in the Region of Transition to the Paramagnetic State

Effect of the temperature on the high-frequency electric impedance of amorphous soft magnetic cobalt-based wires is investigated. A high sensitivity of their impedance to the transition of the ferromagnetic state into the paramagnetic state is demonstrated. The temperature dependences of the impedance measured at different alternating current frequencies allow a distribution of the magnetic phases in the wire volume to be elucidated.