Amorphous Magnetic Alloys Research Articles

Cooling rate upon in air heat treatment and magnetic properties of amorphous soft magnetic alloys

Investigation of the cooling rate effect during heat treatment in air of amorphous magnetic alloys of Fe-Ni-Si-B and Co-Fe-Ni-Cr-Mn-Si-B in states with different signs of saturation magnetostriction were performed to optimize the magnetic properties. It is shown that the increase in cooling rate from 15 to 40 °C/min contributes to the magnetic properties improvement in a state with λs > 0 and their deterioration in a state with λs < 0. This is due to the different influence of induced stresses caused by interaction of ribbon surface with atmospheric water vapor, and their value changes affected by cooling rate change.

Electrical field control of magnetoelectric effect in composite structures with single crystal piezoelectrics

The influence of constant electric field on the characteristics of the direct magnetoelectric effect in composite structures with single crystal piezoelectric layers was observed. The effect was measured in the structures with langatate and catangasite piezoelectric layers and amorphous magnetic alloy metglas as a ferromagnetic layer. The value of magnetoelectric voltage coefficient of 146 V/(Oe·cm) was obtained for the langatate-based structure and value of 1.35 V/(Oe·cm) for the catangasite-based structure. For the langatate-metglas structure, electrical field of 20 kV/cm resulted in a change in the generated voltage up to 63%, in the quality factor Q up to 76%, and provided linear variation of the resonance frequency up to 16 Hz. Electrical field control of magnetoelectric effect characteristics can be used to design new magnetoelectric devices.

Electrochemical Behavior of an Amorphous and Nanocrystalline Fe79P13Si5V3 Alloy in a Damp SO2-Contaminated Atmosphere

The electrochemical behavior of amorphous and nanocrystalline soft magnetic Fe79P13Si5V3 alloy in a 0.1 M Na2SO4 solution has been studied. Mossbauer studies show that the electrochemical characteristics of the alloy are comparable with those of an Finemet Fe77Si13B7Nb2.1Cu0.9 alloy, whereas the studied alloy is inexpensive and can be prepared using natural alloy ferrophosphorus containing vanadium and silicon.

Development of New Amorphous and Nanocrystalline Magnetic Materials for Use in Energy-Efficient Devices

ABSTRACTFe-based amorphous and nanocrystalline soft magnetic alloys have been intensively researched for many applications, including high efficiency electrical distribution and power conditioning applications. New amorphous foils with a saturation magnetization of 1.63T and new nanocrystalline foils with saturation up to 1.9T have been developed. Often these new materials are not drop-in replacements for the conventional competing alloys and require significant changes in processing to be able to fabricate commercial devices.

Determination of Specific Losses in Stator Core of Electromechanical Energy Converter

The purpose of this paper is the experimental research of the magnetic losses in electrical steels, soft magnetic alloys and amorphous alloys in the wide range of the magnetization reversal frequency and magnetic induction. The comparison between different analytical calculation methods of the stator-core specific losses is presented. The article shows that the known methods with the sufficient accuracy allows the stator-core-specific-loss calculation at frequencies below 400 Hz. However, the discrepancy with the calculations of losses by the different methods at the higher frequencies (above 400 Hz) can reach 2 times. The experimental research at high frequencies showed the 2-3-time discrepancy between the calculated and experimental data.

The influence of periodical, interference laser micromachining on nano-crystallization of amorphous magnetic ribbons

The main problem connected with crystallization of amorphous magnetic materials from the FeSiB(X) group is the increase of their fragility with the increasing content of crystalline phase. To overcome this defect the possibilities offered by the interference, pulse laser heating of FeSiB ribbons were utilized. A simple, interference prismatic system at the output of Nd:YAG laser (8-10 ns, 2 J, 1064 nm) was used. The investigations included the influence of laser radiation energy density, number of laser pulses and their periodical, spatial surface arrangement on the crystallization process. Full Text: PDF ReferencesY.R. Zhang and R.V. Ramanujan, "A study of the crystallization behavior of an amorphous Fe77.5Si13.5B9 alloy", Mater. Sci. Eng. A 416, 161 (2006). CrossRef T. Alam, T. Borkar, S. Joshi, S. Katakamb, X. Chenc and N.B. Dahotre, "Influence of niobium on laser de-vitrification of Fe-Si-B based amorphous magnetic alloys", J. Non-Cryst. Solids 428, 75 (2015). CrossRef K.G. Pradeep, G. Herzer, P. Choi and D. Raabe, "Atom probe tomography study of ultrahigh nanocrystallization rates in FeSiNbBCu soft magnetic amorphous alloys on rapid annealing", Acta Mater. 68, 295 (2014). CrossRef S. Katakam, J.Y. Hwang, H. Vora, S.P. Harimkar, R. Banerjee and N.B. Dahotre, "Laser-induced thermal and spatial nanocrystallization of amorphous Fe-Si-B alloy", Scr. Mater. 66, 538 (2012). CrossRef J. Kusiński, A. Sypień, G. Kusiński and C. Nilson, "Microstructure and nanochemistry of Ca-doped cobalt oxide single crystals", Mat. Chem. Phys. 81, 390 (2003). CrossRef C. Smith, S. Katakam, S. Nag, X. Chen, R.V. Ramanujan, N.B. Dahotre and R. Banerjee, "Improved soft magnetic properties by laser de-vitrification of Fe-Si-B amorphous magnetic alloys", Mater. Lett. 122, 155 (2014). CrossRef Ch. Lu and R. H. Lipson, "Interference lithography: a powerful tool for fabricating periodic structures", Laser Photonics Rev. 4, 568 (2010). CrossRef K. Czyż, J. Marczak, R. Major, A. Mzyk, A. Rycyk, A. Sarzyński and M. Strzelec, "Selected laser methods for surface structuring of biocompatible diamond-like carbon layers", Diam. Relat. Mater. 67, 26 (2016). CrossRef A. Sarzyński, J. Marczak, M. Strzelec, A. Rycyk, K. Czyż and D. Chmielewska, "Laser micro-structuring of surfaces for applications in materials and biomedical science", Proc. SPIE, 10159, 101590A (2016). CrossRef

Formation of soft magnetic high entropy amorphous alloys composites containing in situ solid solution phase

Fe-Co-Ni-Si-B high entropy amorphous alloys composites (HEAACs), which containing high entropy solid solution phase in amorphous matrix, show good soft magnetic properties and bending ductility even in optimal annealed state, were successfully developed by melt spinning method. The crystallization phase of the HEAACs is solid solution phase with body centered cubic (BCC) structure instead of brittle intermetallic phase. In addition, the BCC phase can transformed into face centered cubic (FCC) phase with temperature rise. Accordingly, Fe-Co-Ni-Si-B high entropy alloys (HEAs) with FCC structure and a small amount of BCC phase was prepared by copper mold casting method. The HEAs exhibit high yield strength (about 1200 MPa) and good plastic strain (about 18%). Meanwhile, soft magnetic characteristics of the HEAs are largely reserved from HEAACs. This work provides a new strategy to overcome the annealing induced brittleness of amorphous alloys and design new advanced materials with excellent comprehensive properties.

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 of magnetic Ni-P amorphous alloy microspheres and their catalytic performance towards thermal decomposition of ammonium perchlorate

In this work, a series of amorphous Ni-P alloys with diverse microspheric structures and magnetic properties were successfully prepared through a facile aqueous solution reduction using sodium hypophosphite as reducing agent with the assistance of polyvinylpyrrolidone (PVP). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and laser particle size analysis were used to investigate the structure of Ni-P alloy particles, which demonstrated that the as-prepared alloys possessed spherical morphologies and tunable compositions. We investigated the effects of the synthesis conditions including reaction temperature, initial Ni2+ concentration, pH value, and surfactant type on the morphologies and chemical constitutes of Ni-P alloy particles. Compared with other microsphere counterparts (ferromagnetism), the spherical Ni-P alloy powders with diameter of about 500nm exhibited apparent paramagnetism. In addition, the catalytic performance of the products on the thermal decomposition of ammonium perchlorate (AP) was further investigated via thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). These Ni-P noncrystalline alloy particles with different magnetic properties and good catalytic activities would broaden the technological and industrial applications of Ni-P alloys in petrochemical reaction, soft magnetic devices, and burning rate catalysts.

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.

EMCD with an electron vortex filter: Limitations and possibilities

We discuss the feasibility of detecting spin polarized electronic transitions with a vortex filter. This approach does not rely on the principal condition of the standard electron energy-loss magnetic chiral dichroism (EMCD) technique, the precise alignment of the crystal in order to use it as a beam splitter, and thus would pave the way for the application of EMCD to new classes of materials and problems, like amorphous magnetic alloys and interface magnetism. The dichroic signal strength at the L2, 3-edge of ferromagnetic Cobalt (Co) is estimated on theoretical grounds using a single atom scattering approach. To justify this approach, multi-slice simulations were carried out in order to confirm that orbital angular momentum (OAM) is conserved in amorphous materials over an extended range of sample thickness and also in very thin crystalline specimen, which is necessary for the detection of EMCD. Also artefact sources like spot size, mask tilt and astigmatism are discussed. In addition, the achievable SNR under typical experimental conditions is assessed.

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.