Fe-based Glassy Alloys Research Articles

Effect of casting vacuum on thermodynamic and corrosion properties of Fe-based glassy alloy

The effect of casting vacuum on thermodynamic and corrosion properties of Fe61Co7Zr8Mo5W2B17 in shape of cylinder of 3 mm in diameter and ribbon of 20–40 μm in thickness and 2–3 mm in width were investigated with X-ray diffraction (XRD), differential scanning calorimetry (DSC), dilatometer (DIL), scanning electron microscopy (SEM) and electrochemical station. It is found that high casting vacuum can improve the glass forming ability (GFA), the contraction degree during heating, and the pitting resistance of the glassy alloy, which can be ascribed to the fact that the dissolution of tungsten in the melt is improved under the high casting vacuum.

Syntheses and corrosion behaviors of Fe-based amorphous soft magnetic alloys with high-saturation magnetization near 1.7 T

Abstract

Chemical vapor deposition synthesis of carbon nanospheres over Fe-based glassy alloy particles

A mass of carbon nanospheres (CNSs) have been synthesized by chemical vapor deposition of C2H2 directly over Fe-based glassy alloy particles (Fe76Si9B10P5) without the addition of an external catalyst. The morphology and microstructure as well as the growth mechanism of the CNSs have been investigated by using scanning and transmission electron microscopy. The results showed that the obtained products consist of hollow CNSs and CNSs with Fe nanoparticles encapsulated. The CNSs with amorphous walls have high purity (>95%) and uniform size distribution (50–150nm). The possible formation and growth mechanism of the CNSs were discussed on the basis of the investigation on their initial growth stages.

Thermopower Monitoring of Relaxation and Devitrification in Fe-Based Glassy Alloys

The change of thermopower is investigated in Fe-based glassy alloys during structural relaxation and amorphous-crystalline transformation. It was found, that thermopower shifts to negative direction until solely the relaxation proceeds. This negative shift is composition independent. The net shape of thermopower curves is composed from the thermopower of the individual constituent crystalline phases after the crystallization process.

Pronounced enhancement of glass-forming ability of Fe–Si–B–P bulk metallic glass in oxygen atmosphere

Abstract

Crystallization kinetics of Co40Fe22Ta8B30 glassy alloy with high thermal stability and soft magnetic properties

In this paper, the thermal stability, the crystallization kinetics and magnetic properties of the melt-spun Co40Fe22Ta8B30 glassy alloy were investigated. The results show that the present alloy has a wide supercooled liquid region of 74K and a high incubation time prior to crystallization upon isothermal annealing above the glass transition temperature compared to the well-known Co43Fe20Ta5.5B31.5 glassy alloy. The crystallization kinetics was systematically investigated by the Kissinger, Ozawa and isoconversional approaches under the isochronal condition, and Johnson–Mehl–Avrami (JMA) model under the isothermal situation, respectively. It was found that the Co40Fe22Ta8B30 metallic glass indicated an apparent activation energy of 520±5kJ/mol corresponding to the first crystallization event, which is higher than many other Fe-based and Co-based glassy alloys. The Avrami exponent calculated based on the JMA approach lies in the range of 2.13–1.58 for different isothermal annealing temperatures, revealing that the crystallization is governed by the three-dimensional diffusion-controlled growth with a decreasing nucleation rate. In addition, Co40Fe22Ta8B30 metallic glass exhibits good soft magnetic properties, i.e. a very low coercivity of 0.8A/m and a magnetization of 42Am2/kg. The influence of the devitrification on the evolution of the coercivity, magnetization and thermomagnetic behavior of Co40Fe22Ta8B30 glassy alloy was investigated.

Iron-based bulk metallic glasses

The current status of research and development in Fe-based bulk metallic glasses (BMGs) is reviewed. Bulk metallic glasses are relatively new materials possessing a glassy structure and large section thickness. These materials have an exciting combination of properties such as high mechanical strength, good thermal stability, large supercooled liquid region and potential for easy forming. Ever since the first synthesis of an Fe-based BMG in an Fe–Al–Ga–P–C–B system in 1995, there has been intense activity on the synthesis and characterisation of Fe-based BMGs. These BMGs exhibit some unique characteristics which have not been obtained in conventional Fe-based crystalline alloys. This uniqueness has led to practical uses of these bulk glassy alloys as soft magnetic and structural materials. This review presents the recent results on the glass-forming ability, structure, thermal stability, mechanical properties, corrosion behaviour, soft magnetic properties and applications of Fe-based bulk glassy alloys developed during the last 15 years. This review also highlights the advanced analysis of their properties which has contributed significantly to the progress in understanding and developing of the Fe-based BMGs. The future prospects of Fe-based BMGs have also been presented.

Overspray Powder Characterization of Fe-Based Glassy Alloy

Powder of Fe72Nb4Si10B14 (%at) glassy alloy was obtained by gas atomization in order to investigate the possibilities of amorphous phase formation due to the high cooling rates (103 105 K/s) involved in this process. The ratio between the gas volumetric and the metal mass flow rates used was 1.0, and nitrogen (N2) was used as the atomization gas. The powder, sieved in different granulometric size ranges, was characterized through: X-ray diffratometry (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Fe72Nb4Si10B14 (%at) bulk metallic glass (BMG) showed completely or partially glassy structure depending on the size range. The obtaining of powders with glassy structure that could be applied as shot penning powder particles and thermal spray feeding powder for metallic coatings or would make possible the production of bulk glassy materials by warm consolidation of such powders or even a millimeters thick deposit obtained by spray forming with glassy or metastable microstructure that would be very interesting considering applications as soft ferromagnetic parts.

Crystallization and Corrosion Resistance of (Fe 0.78Si 0.09B 0.13) 100- xNi x ( x=0, 2 and 5) Glassy Alloys

The crystallization of the (Fe0.78Si0.09B0.13)100-xNix glassy alloys (x=0, 2 and 5) has been investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). Corrosion resistance analyses have been carried out using electrochemical measurements and corrosion products have been analyzed by scanning electron microscopy (SEM). The experimental results show that the addition of Ni can promote the nucleation of α-Fe, retard the decomposition of the metastable borides, and alter the crystallization mode of the present Fe-based glassy alloys. The lattice constant (αFe0) of α-Fe in the annealed samples shows a decreasing trend with increasing annealing time. The Ni addition can improve the corrosion resistance of the as-quenched Fe-based glassy alloys in H2SO4, NaCl and NaOH solutions. The results indicate that Ni can promote the diffusion of Si atoms during quenching and annealing processes.

SiC dispersed Fe-based glassy composite cores produced by spark plasma sintering and their high frequency magnetic properties

Using the mixtures of the gas-atomized Fe-based glassy alloy powders blended with ceramic SiC particulates, toroidal shape Fe-based metallic glassy alloy composite cores were produced by the spark plasma sintering (SPS) process. The effect of the SiC particulates on the high frequency magnetic properties of the fabricated composite cores was investigated. The Fe-based metallic glassy alloy cores obtained by the SPS process exhibited high density and excellent soft magnetic properties. The addition of the SiC particulates was effective in improving high frequency magnetic properties.

Fe-based glassy alloys with high iron content and high saturation magnetization

Iron-based bulk metallic glasses (BMGs) are attractive due to their excellent magnetic properties. It is known that increasing the iron content in alloys would enhance the magnetic property of glassy alloys, but would reduce their glass forming ability. Despite researchers are keen to develop Fe-based BMGs with high Fe content, BMG with Fe content higher than 79 at.% has not been reported. Here we report that Fe-based BMGs with Fe content as high as 78 ∼ 81 at.% have been successfully prepared. The as-prepared Fe81Mo1P7.5C5.5B2Si3 BMG possesses a saturation magnetization of 1.64 T, which is significantly higher than the reported value in BMGs.

Vibrational dynamics of Fe-based glassy alloys

The well recognized model potential is used to investigate the vibrational properties of four Fe-based binary glassy alloys viz. Fe90Zr10, Fe80B20, Fe83B17 and Fe80P20. The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves (PDC). Three theoretical approaches given by Hubbard-Beeby (HB), Takeno-Goda (TG) and Bhatia-Singh (BS) are used in the present study to compute the PDC. Six local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) and Sarkar et al.’s local field factor (SLFF) based excgange and correlation function are employed to see the effect of exchange and correlation in the aforesaid properties.

Casting vacuum effects on the precipitates and magnetic properties of Fe-based glassy alloys

The crystalline precipitates and magnetic properties of the Fe 61Co 9 − x Zr 8Mo 5W xB 17 (x = 0 and 2) cylinders prepared under various vacuum conditions were investigated in this paper. The fraction of the crystalline precipitates and liquidus temperature of the samples with tungsten content c W = 0 decease with decreasing vacuum, while they increase in the samples with c W = 2 at.%. For both tungsten contents, with decreasing vacuum, the magnetization at room temperature M start and Curie temperature T h c of the samples decrease gradually, but the increment of magnetization Δ M 800 K at 800 K after heating to 973 K increases and the Curie temperature T c c of the residual amorphous matrix shows a decreasing tendency simultaneously. Meanwhile, with decreasing vacuum, Zr–B compounds tend to precipitate easily out from the melt or to remain undissolved during casting, and eutectic Fe–B compounds tend to be formed easily after heating to 973 K. The existence of Zr–B and Fe–B compounds changes the boron content in the residual melt/matrix and consequently affects the magnetic properties of the samples in the as-quenched state and after heating to 973 K.

Novel FePBNbCr glassy alloys “ SENNTIX” with good soft-magnetic properties for high efficiency commercial inductor cores

According to a recent study, Fe-based glassy alloys are expected good soft-magnetic properties such as high saturation magnetization and lower coercive force. We focused on Fe-based glassy alloys and have succeeded in developing novel glassy Fe 97− x− y P x B y Nb 2Cr 1 ( x = 5–13, y = 7–15) alloys for an inductor material. The glassy alloy series of Fe 97− x− y P x B y Nb 2Cr 1 ( x = 5–13, y = 7–15) have high glass-forming ability with the large critical thickness of 110–150 μm and high B s of 1.25–1.35 T. The glassy alloy powder with chemical composition Fe 77P 10.5B 9.5Nb 2Cr 1 exhibits an excellent spherical particle shape related to the lower melting point and liquid phase point. In addition, Fe–P–B–Nb–Cr powder/resin composite core has much lower core loss of 653–881 kW/m 3, which is approximately 1/3 lower than the conventional amorphous Fe–Si–B–Cr powder/resin composite core and 1/4 lower than the conventional crystalline Fe–Si–Cr powder/resin composite core due to the lower coercive force of 2.5–3.1 A/m. Based on above results, the glassy Fe 77P 10.5B 9.5Nb 2Cr 1 alloy powder enable to achieve ultra-high efficient and high quality products in a commercial inductor. In fact, the surface mounted inductor using Fe–P–B–Nb–Cr powder/resin exhibits the high efficiency of approximately 2.0% compared with the conventional inductors made of the crystalline Fe–Si–Cr powder/resin composite core.

Recent Development and Applications of Bulk Glassy Alloys

This paper reviews past developments and the present understanding of the physical and mechanical properties of glass alloys, with an emphasis on recent results obtained since around 1990, together with applications of bulk glassy alloys achieved mainly in Tohoku University. After introducing the fundamental concepts around glassy alloys in the first section, the second section describes the relationships between structural relaxation and the discoveries of glassy alloys with a large supercooled liquid region. The third section reviews the history of bulk glassy alloy development, followed by the bulk glassy alloy systems and their features in the fourth section and the features of a glassy structure in the fifth section. The sixth, seventh, and eighth sections summarize the engineering and standardization of Zr‐based bulk glassy alloys. Section nine and the 10th focus on the glass‐forming ability of Zr‐based hypoeutectic glassy alloys and Cu–Zr–Al–Ag bulk glassy alloys. The mechanical properties of Ni‐based bulk glass alloys at low temperatures are shown in the 11th section, whereas the 12th section describes the formation and properties of Ni‐free Ti‐based bulk glassy alloys. The 13th and 14th sections deal with porous Zr‐based bulk glassy alloys including spherical pores and commercialized Fe‐based glassy alloys, respectively, whereas the 15th section reviews supercoold liquid forming. Finally, applications for Zr‐, Ti‐, and Fe‐based glassy alloys are described in the 16th section. In conclusion, the 17th section attempts to assess the present knowledge of the structure and physical properties and identify some outstanding problems for future work.

FePBNbCr Soft Magnetic Glassy Alloys <i>“SENNTIX”</i> with Low Loss Characteristics for Commercial Inductor Cores

The inductor for a power supply is expected to have higher efficiency and capability of dealing satisfactorily with large current. Additionally, high corrosion resistance characteristics are also required for commercial inductors in practical use of. Thereby, we focused on Fe-based glassy metal alloys with both high magnetization and low magnetic anisotropy ［1］, and developed the novel glassy metal alloys with a chemical composition Fe97-x-yPxByNb2Cr1. In this glassy metal alloy, 1 at % Cr is the optimum composition for the realization of higher corrosion resistance as well as a high magnetic flux density. The glassy Fe97-x-yPxByNb2Cr1 (x=5-13, y=7-15) alloy exhibits the high glass-forming ability leading to the large thickness of 110-150 μm and low coercive force of 2.5-3.1 A/m due to higher structural homogeneity in wide range of composition. The large critical thickness of this alloy should be caused by the high glass-forming ability (GFA) due to the existence of the super cooled liquid region (Tx) of roughly 30 K. Therefore a Fe77P7B13Nb2Cr1 powder/resin composite core displays a much lower core loss of 650 W/m3 than the conventional amorphous Fe75Si10B12Cr3 powder/resin composite core by approximately 1/3.

Effect of Zr on the thermal stability and magnetic properties of Fe 78Si 9B 13 glassy alloy

The (Fe 0.78Si 0.09B 0.13) 100− x Zr x ( x = 0, 1 and 2) glassy alloys have been investigated in this paper. The experimental results show that the minor addition of Zr can improve the thermal stability of the Fe-based alloy. The thermal contraction process of the ribbons is mainly dependent on the crystallization process. With increasing Zr content ( c Zr), the difference (Δ d) between the nearest neighbor distance ( d exp) deduced from the X-ray diffraction pattern and the estimated nearest neighbor distance d cal, the onset crystalline temperature ( T x), the reduced crystalline temperature ( T rx), the apparent activation energy ( E p1) for the first crystallization, and the difference (Δ α) between the expansion coefficients of amorphous ribbons ( α amor) and fully crystallized counterparts ( α cryst) of the Fe-based glassy alloys first increase and then decrease, which is opposite to the change of the saturation magnetization ( M s). The variation of these parameters can be explained by the deviation degree from the equilibrium state of the amorphous ribbons. Besides the M– T measurement, the Curie temperature ( T c) of the Fe-based glassy alloys can also be scaled by the bump and inflection temperatures ( T c,dsc and T k) in differential scanning calorimetric and dilatometric curves, respectively, showing a slight decreasing tendency with increasing c Zr.

FePBNbCr soft-magnetic glassy alloys with low loss characteristics for inductor cores

Fe-based glassy alloys with both high saturation magnetization and low magnetic anisotropy have attracted interest in recent study on Mr. Inoue, 2004, and we have succeeded in developing novel glassy Fe 97− x− y P x B y Nb 2Cr 1 ( x = 5–13, y = 7–15) alloys for an inductor material. The glassy alloy series of Fe 97− x− y P x B y Nb 2Cr 1 ( x = 5–13, y = 7–15) have high glass-forming ability with the large critical thickness of 110–150 μm and low coercivity of 2.5–3.1 A/m caused by the structural homogeneity. The Fe 77P 7B 13Nb 2Cr 1 glassy alloy exhibits the largest critical thickness of 150 μm related to the wide super cooled liquid region and the high saturation magnetic flux density ( B s ) of 1.3 T, both of which are higher than those of the conventional amorphous Fe 75Si 10B 12Cr 3 alloy. Hence, Fe–P–B–Nb–Cr powder/resin composite core has much lower core loss of 650 kW/m 3 which is approximately 1/3 lower than the conventional amorphous Fe–Si–B–Cr powder/resin composite core that are annealed at 623 K. In addition, the optimum annealing temperature of 623 K for these glassy alloys was lower than that (723 K) for the ordinary Fe–Si–B–Cr amorphous alloy, which is a significant advantage for the efficiency in mass production of inductor core using soft-magnetic glassy alloy powder.

Novel ${\hbox {Fe}}_{(97-{\rm x-y})}{\hbox {P}}_{\rm x}{\hbox {B}}_{\rm y}{\hbox {Nb}}_{2}{\hbox {Cr}}_{1}$ Glassy Alloys With High Magnetization and Low Loss Characteristics for Inductor Core Materials

Fe-based glassy alloys with both high saturation magnetization and low magnetic anisotropy have attracted interest recently , and we have succeeded in developing novel glassy Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(97-x-y)</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> (x=5 -13, y=7-15) alloys for an inductor material with high corrosion resistance by added Cr is 1 at%. The glassy alloy series of Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(97-x-y)</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cr (x=5-13, y=7-15) have high glass-forming ability with wide range super-cooled liquid region of 29-37 K, large critical thickness of 110-150 ¿m, and low coercivity of 2.5-3.1 A/m caused by the structural homogeneity. The Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">77</sub> P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sub> Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> glassy alloy exhibits the largest critical thickness of 150 ¿m related to the wide super-cooled liquid region of 36 K and the high saturation magnetic flux density (Bs) of 1.3 T, both of which are higher than those of the conventional amorphous Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">75</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> alloy. The Fe-P-B-Nb-Cr powder/resin composite core has much lower core loss of 650 kW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> which is approximately 1/3 lower than the conventional amorphous Fe-Si-B-Cr powder/resin composite core annealed at 623 K. Additionally, The Fe-P-B-Nb-Cr glassy alloy has higher corrosion resistance than other system glassy metal of Fe-Si-B-Nb-Cr by having a thick chromium passivation layer. the optimum annealing temperature of 623 K for these glassy alloys is lower than that (723 K) for the ordinary Fe-Si-B-Cr amorphous alloy, which is a significant advantage for the efficiency in mass production of inductor core using soft magnetic glassy alloy powder.

Effect of Mo element on the properties of Fe–Mo–P–C–B bulk metallic glasses

Abstract Bulk Fe80−xMoxP10C7.5B2.5 (x = 5–10 at.%) metallic glasses are synthesized by copper mold casting, which have a critical diameter up to 3 mm, fracture strength over 3000 MPa, plastic strain up to 2.5% and saturation magnetization reaching 1.1 T. Results show that the glass forming ability and strength increase with increasing Mo content, while the plasticity and saturation magnetization do otherwise. These Mo content dependent properties are illuminated with the atomic interactions in the alloys that could be strengthened by suitable addition of Mo element. The effects of Mo on the properties of the alloys imply that proper Mo element should be chosen in designing Fe-based glassy alloys with desired properties.