Amorphous Magnetic Alloys Research Articles

Study of crystallization behavior and kinetics of magnetic FeCoCrNiZr high entropy amorphous alloy

A new magnetic Fe36Co22Cr17Ni15Zr10 high entropy amorphous alloy has been prepared and its crystallization behavior and kinetics been studied. The results show that, under non-isothermal conditions, the crystallization activation energy Ex was calculated by the Kissinger equation, which yield 373 kJmol−1. Relation plot of Ex vs crystallization volume fraction(x) manifests the non-isothermal crystallization process is from difficult to easy. On the other hand, base on Arrhenius relation, the crystallization activation energy Ec under isothermal conditions was calculated to be 370 kJmol−1. Relation plot of Ec vs x manifests the isothermal crystallization process is from easy to difficult. The isothermal kinetics was modeled by Johnson-Mehl-Avrami(JMA) equation, as the isothermal annealing temperature increases, the nucleus growth mechanism from diffusion-controlled 3-D growth convert into interface-controlled 3-D growth. Though proper heat treatment, the saturation magnetization Ms of this alloy can reach up to 106.8A∙m2∙kg−1, it will become promising functional materials in the future.

Consequences of aging on ferromagnetic amorphous Fe75Si10B15 microwires for advanced inductive applications

Amorphous ferromagnetic microwires fabricated by water-quenching have been assessed to show favorable properties for next-generation high-frequency electric machines as compared to those of conventional amorphous magnetic alloys in sheet or ribbon form. Here, water-quenched amorphous Fe75Si10B15 microwires were subjected to a range of aging times of up to 5 years in the air at room temperature. While both newer and aged microwires are X-ray amorphous, the aged microwires do exhibit a slight degree of crystallinity, a lower initial susceptibility and a reduced enthalpy change for full devitrification. These small differences (typically < 5%) are attributed to the formation of minor surface oxidation products such as iron oxides and SiO2 which modify the surface strain state. The resultant stress couples to magnetostriction to promote the formation of radial magnetic domains that impair the magnetic reversal process. These results demonstrate that while amorphous ferromagnetic microwires are essentially stable against aging in the air, consideration of their surface state will be significant for advanced applications.

Correlations between the thermal properties and the electronegativity of soft magnetic Fe-based amorphous alloys

In this letter, we report clear correlations between the glass transition temperature Tg, the crystallization temperature Tx, the Curie temperature TC and the electronegativity based on statistically analyzing more than 200 kinds of soft magnetic Fe-based amorphous alloys. The underlying physical origin of these correlations is discussed. Based on these correlations, the influences of various alloying elements are classified. These results are helpful for designing new soft magnetic amorphous alloys with high thermal stability.

Effect of C addition on the corrosion properties of amorphous Fe-based amorphous alloys

Fe-based amorphous alloys are important materials with a high potential for commercialization by evaluating their corrosion performances. In this work, amorphous Fe[Formula: see text]Cu1Nb3Si[Formula: see text]B9 alloy was chosen as a target material to investigate the effects of the addition of C on the corrosion properties by an electrochemical method. Alloy ingots Fe[Formula: see text]Cu1Nb3Si[Formula: see text]C[Formula: see text]B[Formula: see text] (x = 0, 1, 2, 3 at.%) were prepared using an arc melting system, under argon atmosphere. Planar flow melt spinning of the alloys was carried out to obtain amorphous ribbons of the width [Formula: see text][Formula: see text]5 mm and the thickness about 30 [Formula: see text]m. Effects of the addition of C into Fe[Formula: see text]Cu1Nb3Si[Formula: see text]B9 amorphous soft magnetic alloys were investigated in acidic solutions. Studies of potentiodynamic polarization and electrochemical impedance revealed the passivation ability and corrosion resistance of the amorphous ribbons with C in the 0.1M H2SO4 media at room-temperature. The amorphous ribbons showed excellent corrosion resistance with formation of a stable passive film. It can be obviously observed that the addition of C significantly improves the corrosion resistance.

Scaling of Minor Hysteresis Loops in Soft Magnetic Amorphous Alloy

Scaling of minor hysteresis loops in the amorphous alloy Co66Fe3Cr3Si15B13with a very high initial permeability (more than 150000) and low coercivity (about 0.1 А/m) has been studied. In weak magnetic fields and in the region of maximal growth of permeability a similarity of minor loops was detected. Analytical expressions for hysteresis losses are derived which provide a good accordance of calculations with the results of measurements.

Preparation and degradation property of magnetic FePBCSi amorphous alloy powder

The effects of metalloid admixture on the amorphous forming ability (AFA) of the Fe100-4xPxBxCxSix (x = 7, 8, 9, 10) alloy powders, which are prepared by mechanical alloying technology, are investigated by means of X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the AFA and the magnetic properties of the alloy powders can be improved with proper metalloid admixture, among which the amorphous Fe72P7B7C7Si7 alloy powder with high saturation magnetization and low coercivity can be obtained. The amorphous Fe72P7B7C7Si7 alloy powder also exhibits good capability in degrading methylene blue dyes, and the optimal conditions for degradation processing are explored.

A new soft magnetic Fe75Ta5C20 amorphous alloy: Modelling and kinetics approach

In this study, a new soft magnetic Fe75Ta5C20 amorphous alloy was fabricated through mechanical alloying. The microstructure evolution, magnetic properties and thermal behavior were investigated versus milling time by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transition electron microscopy (HRTEM), vibrating sample magnetometer (VSM) and differential scanning calorimetry (DSC). The results of the study showed, the highest amorphous phase fraction of about 94% was obtained after 70 h of milling. As an innovative approach, an applicable mathematical model was proposed to anticipate the saturation magnetization value with milling time. The prediction capability of the model was outstanding, which were validated by fitting to the results of other studies. Finally, the non-isothermal crystallization kinetics of the 70 h milled sample was studied by Kissinger and Ozawa methods. The apparent activation energies of 591 and 346 kJ/mol were obtained using Kissinger method for the nucleation and growth processes, respectively.

Soft magnetic properties of Fe82-83B14-15Si2C0.5-1 amorphous alloys with high saturation magnetization above 1.7 T

With the aim of developing a new inexpensive soft magnetic amorphous alloy exhibiting high saturation magnetic flux density (Bs) above 1.7 T, we examined the formation, thermal stability and magnetic properties for melt-spun Fe-B-Si-C amorphous alloys with high (B + C)/Si content ratios. The high Bs of 1.71–1.73 T exceeding the previously reported Bs was obtained for annealed Fe82-82.5B15Si2C0.5-1 alloys. These high Bs alloys exhibit low coercivity below 8 A/m and good bending ductility. The 82.5Fe alloy with the highest Bs of 1.73 T also has the highest hardness. Besides, the 82.5Fe alloy has the largest nearest neighbor atomic distance among the present alloys. The correlation between the highest Bs and the largest atomic distance is similar for (Fe,Co)83-86B15-16Si1 amorphous alloys. The 82.5Fe and 82Fe alloys are located near the critical composition where the crystallization changes from two stages of α-Fe(Si) + amorphous ⇢ α-Fe(Si) + Fe3(B,C) to a single stage of α-Fe(Si) + Fe3(B,C). These results indicate the importance of the special alloy composition with the largest atomic distance and high stability to primary α-Fe precipitation, in addition to high (B + C)/Si content ratios, for the synthesis of a new ductile amorphous alloy with high Bs and good magnetic softness.

Highly Ductile and Ultra-Thick P-Doped FeSiB Amorphous Alloys with Excellent Soft Magnetic Properties.

Herein, we demonstrate the successful synthesis of novel Fe80Si9B(11−x)Px (x = 0, 1, 3, 5, 7) ultra-thick amorphous ribbons by planar flow casting. The influence of P alloying on glass forming ability (GFA), microstructure, thermal stability, soft magnetic properties, and ductility has been systematically investigated. The results reveal that introduction of P into Fe80Si9B11 alloy can remarkably enhance the GFA and increase critical thickness (tc) of the alloy from 45 to 89 um. Furthermore, the annealed FeSiBP amorphous alloys exhibited excellent soft magnetic properties, including high saturation magnetic flux density of 1.54 T, the low coercivity of 1.5 A/m, and low core losses of 0.15 W/kg. In addition, the representative Fe80Si9B8P3 ultra-thick amorphous alloy demonstrate excellent ductility even after annealing at 400 °C for 10 min, which indicates the superior performance of P-doped FeSiB alloys as compared to the commercial Fe78Si9B13 (Metglas 2605 S2) alloy. The combination of high GFA, excellent ductility, and low core losses of newly developed FeSiBP amorphous soft magnetic alloys makes them attractive candidates for magnetic applications in the high-frequency and high-speed electric devices.

Magnetic field annealing of FeCo-based amorphous alloys to enhance thermal stability and Curie temperature

Annealing temperatures and applied magnetic fields are two important parameters for the performance modification of magnetic alloys. This article investigated the effect of different annealing temperatures on crystallization condition, magnetic properties and thermal stability of the amorphous magnetic alloy Co36Fe36Si4.8B19.2Nb4 (at%). Results indicate that the annealing temperature can significantly affect the size and content of precipitated nanocrystals in the amorphous alloy, and the precipitation of nanocrystalline phases can result in the distinct change of magnetic properties and Curie temperature. When the annealing was performed at 595 °C for 30 min under an applied transverse external magnetic field of 9550.0 A·m−1, the amorphous alloy shows excellent soft magnetic properties with the saturation magnetization of alloy reaching 110.00 mA·m2·g−1, the residual magnetic induction intensity of 4 × 10−6 T and the coercivity as low as 57.3 A·m−1. Furthermore, the Curie temperature of the field-annealed samples can reach up to 440 °C, approximately 58 °C higher than that of the as-quenched species.

STRUCTURE FEATURES OF THE Fe –Cu–Nb–Si–B BASED NANOCRYSTALLINE ALLOY RIBBON PRODUCED BY THE MELT SPINNING METHOD

Amorphous and nanocrystal magnetic soft Fe-based alloys are widely used for the shielding materials production, which are effective in the wide range of magnetic and electromagnetic fields. These alloys are obtained in ribbons by an ultra-quick quenching of the melt flow on the high-speed rotating refrigerator-disk. During the amorphous ribbons production process, melted in the high-frequency inductor metal is fed through the dye on the surface of the quenching disk, wherein the surface layers, contacted with the refrigerator-disk, of the forming amorphous ribbon are cooled quicker than the top ones, which are not in contact with the refrigerator-disk. As the result on the “contact” side of the ribbon the residual compression stresses can occur, wherein on the “free” side – the tension stresses. All these can lead to the structure anisotropy along the ribbon thickness, therefore also to the properties anisotropy during the further heat treatment. In the present paper, the results of the TEM structure analysis (planar geometry and transversal cut geometry) along the ribbon thickness of the AMAG200 alloy (Fe – Nb – Cu – Si – B system), obtained by the spinning method, are presented. The relation between the structure changes in the amorphous AMAG-200 alloy (Fe – Nb – Cu – Si – B system), which occurred during the process of the controlled crystallization, with the structure features of the amorphous ribbon, obtained by the ultra-quick quenching of the melt (with the cooling speed up to 106 K/s) is determined, explaining the structure anisotropy along the ribbon thickness. It is stated that the heat treatment under 530 °С forms high magnetic properties and lowers the destruction energy by the formation of the optimal amorphous-nanocrystallline structure in part of grains volume fraction and size. Using the SEM the fracture appearance analysis was performed, connected to the structure obtained during the ultra-quick quenching from the melt and after the heat treatment under 530 °С. It is stated that the fracture surface at the as-build state provide viscous type and after heat treatment-completely brittle type.

Study of Radioengineering Parameters of Powders of an AMAG-200 Amorphous Soft Magnetic Alloy

The experimental results of studies of radioengineering parameters of a composite based on a powder of an AMAG-200 amorphous soft magnetic alloy of various particle-size fractions have been presented. The influence of the volume ratio of the powder particles in the composite on the microwave properties has been analyzed.

Efficient Catalytic Hydrogenation of Butyl Levulinate to γ-Valerolactone over a Stable and Magnetic CuNiCoB Amorphous Alloy Catalyst

A series of low-cost, magnetic, and high-efficiency CuNiCoB amorphous alloy catalysts were developed by the chemical reduction method for selective hydrogenation of butyl levulinate (BL) to γ-valerolactone (GVL). The catalysts were characterized by inductively coupled plasma optical emission spectrometry, Brunauer–Emmett–Teller, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature-programmed desorption techniques. The results indicated that the CuNiCoB amorphous alloy nanosheets with well-dispersed Cu nanoparticles played an important role in enhancing the hydrogenation activity. The reaction temperature, pressure, time, and substrate concentration were optimized. The maximum GVL yield of 89.5% with BL conversion of 99.7% was achieved over the best Cu0.5Ni1Co3B catalyst using 3 wt % dosage relative to BL at 473 K under 3.0 MPa H2 after 3 h. The considerable stability of Cu0.5Ni1Co3B during catalytic rec...

Magnetization Processes in Ribbons of Soft Magnetic Amorphous Alloys

Using iron-based (Fe–B–Si–C; Fe–Ni–Si–B) and cobalt-based (Co–Fe–Ni–Cr–Mn–Si–B) soft magnetic alloys as examples, we have studied the dependences of the remanence measured using minor hysteresis loops on the maximum induction. The different degrees of stabilization of the 180° and 90° domain walls allows these dependences to be used to analyze the magnetization processes that occur in the rapidly quenched soft magnetic alloys. It has been established from the Br(Bm) dependences that, in the ribbons of soft magnetic amorphous alloys, the processes of the rotation of the magnetization oriented perpendicular to the ribbon plane start before the end of the processes of the displacement of the walls of domains with planar magnetization. After the end of the magnetization rotation processes, the magnetization processes can be interpreted as the displacement of the domain walls with a planar magnetization accompanied by a decrease in their number and a transition to a bistable state.

New methods for probing and exploring magnetoelastic properties of amorphous ferromagnetic alloys

We describe two new methods for investigating and exploring magnetoelastic properties of ribbons of amorphous magnetic alloys. One consists of exciting the ribbon mechanically while detecting the electromagnetic response, and the second method involves the use of a radiofrequency resonator as a contactless technique for measuring magneto-impedance [C. A. Grimes, S. C. Roy, S. Rani, and Q. Cai, Sensors 11, 2809–2844 (2011)]. The electromagnetic response to mechanical vibration is discussed in connection with the possibility of observing Fano resonance in a classical system, and the magneto-impedance is found to be highly sensitive to magnetic domains formation and their dynamics.

Magnetoelectric effect in ferromagnetic-semiconductor layered composite structures

The results of magnetoelectric effect experimental studies in two different structures based on piezoelectric semiconductor gallium arsenide are presented. The monolithic structure consisted of a gallium arsenide substrate with deposited nickel layer (GaAs-Ni), and the composite structure contained a semiconductor substrate with an amorphous magnetic alloy (GaAs-Metglas) ribbon glued on one side. A quality factor Q ≈ 23500 and magnetoelectric coefficient of 316 V/Oe.cm were achieved at the frequency of planar acoustic oscillations for GaAs-Ni structure at room temperature.

Effects of Fe substitution for Co on the thermal, magnetic, and mechanical properties of the Co-Fe-B-Si-Mo alloy system

The effects of Fe content on the thermal, magnetic, and mechanical properties of a Co72B19.2Si4.8Mo4 alloy were studied. Amorphous soft magnetic alloys of (Co1−xFe x )72 B19.2Si4.8Mo4 (0 ≤ x ≤ 1) with 3-mm widths and 27 - 30 μm thicknesses were obtained by using the melt spinning technique. The crystallization temperature (T x ) for each alloy was measured by using differential scanning calorimetry (DSC). All ribbons were identified as fully amorphous by using X-ray diffraction (XRD). The magnetic properties of the amorphous ribbons were measured by using a vibrating sample magnetometer (VSM). The Fe-only ribbon (x = 1) showed the highest saturation magnetization of 1.15 T in these alloys. Also, the nano-hardness (H nanoindentation ), and Young’s modulus (E) were evaluated by using nano-indentation experiments, and Co21.6Fe50.4B19.2Si4.8Mo4 (x = 0.7) show a nano-hardness (H nanoindentation ) of 18.92 GPa.

Research progress and application prospect of Fe-based soft magnetic amorphous/nanocrystalline alloys

Amorphous alloy is a kind of metallic materials prepared by rapidly cooling the alloy melt through hindering crystallization in cooling process. Due to the unique structure of atomic random packing, Fe-based amorphous alloys exhibit not only structural and property isotropy, but also small structural correlation length, small magnetic anisotropic constant, and then small coercivity Hc. Like crystalline Fe-based alloys, Fe-based amorphous alloys also possess high saturation induction Bs. As a result, research on engineering applications of Fe-based amorphous alloys has been promoted by their excellent soft magnetic properties. Now Fe-based soft magnetic amorphous/nanocrystalline alloys have been produced and applied to various areas on a large scale. Here in this paper, the processes of discovery, development and application of Fe-based soft magnetic amorphous alloys are reviewed, and the effects of chemical composition, structure and preparation technology on the soft magnetic properties are introduced and discussed. The obtained theoretic results and the technological innovation show that the great contributions have been made to the development and application of Fe-based soft magnetic amorphous/crystalline alloys. Based on the progress of structure and soft magnetic property and our understanding, the development process of the fundamental research and the application progress of Fe-based soft magnetic amorphous alloys could be divided into three periods. In addition, the present challenge topics in their researches and applications are proposed.

Minor-Cu doped soft magnetic Fe-based FeCoBCSiCu amorphous alloys with high saturation magnetization

The effects of Cu alloying on the amorphous-forming ability (AFA) and magnetic properties of the P-free Fe81Co5B11C2Si1 amorphous alloy were investigated. Addition of ≤ 1.0 at.% Cu enhances the AFA of the base alloy without significant deterioration of the soft magnetic properties. The Fe80.5Co5B11C2Si1Cu0.5 alloy with the largest critical thickness for amorphous formation of ∼35 μm possesses a high saturation magnetization (Bs) of ∼1.78 T, low coercivity of ∼14.6 A/m, and good bending ductility upon annealing in a wide temperature range of 513–553 K with maintaining the amorphous state. The fabrication of the new high-Fe-content Fe-Co-B-C-Si-Cu amorphous alloys by minor doping of Cu gives a guideline to developing high Bs amorphous alloys with excellent AFA.

Soft magnetic amorphous alloys (Fe-rich) obtained by gas atomisation technique

We report a research describing a new route for the production of Fe-Si-B powders, which is the so-called gas atomisation technology, being one of the challenges to study the conditions under which the glass structure is achieved. There have been produced powders of five different compositions in the Fe-Si-B ternary system. The particles with a diameter below 10 μm of the alloy Fe70Si18B12 (at%) were completely amorphous, exhibiting an excellent soft magnetic behaviour (coercivity of around 7 Oe), which is, without any doubt, of significant scientific merit and supports the use of this new route to produce soft amorphous magnetic materials.