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Abstract The microstructural evolution of Fe-6.5 wt.% Si alloy during rapid solidification was studied over a quenching rate of 4 × 104 K/s to 8 × 105 K/s. The solidification and solid-state diffusional transformation processes during rapid cooling were analyzed via thermodynamic and kinetic calculations. The Allen-Cahn theory was adapted to model the experimentally measured bcc_B2 antiphase domain sizes under different cooling rates. The model was calibrated based on the experimentally determined bcc_B2 antiphase domain sizes for different wheel speeds and the resulting cooling rates. Good correspondence of the theoretical and experimental data was obtained over the entire experimental range of cooling rates. Along with the asymptotic domain size value at the infinite cooling rates, the developed model represents a reliable extrapolation for the cooling rate > 106 K/s and allows one to optimize the quenching process. Highlights • New Fe-6.5 wt.% Si melt spinning experiments and cooling rate measurements. • The melt spun ribbons were characterized using TEM analysis. • Solidification and solid-state transformation during rapid quenching were analyzed. • The bcc_B2 domain growth was modeled using the Allen-Cahn theory. [ABSTRACT FROM AUTHOR]

Abstract Two metallurgical purification techniques, namely solvent refining and slag treatment, were combined to remove boron from silicon. Silicon was alloyed with iron and the alloy was subjected to slag treatment by a ternary of CaO-SiO 2 -Al 2 O 3 at 1600 °C (1873 K). Effects of oxygen potential and basicity of slag on boron removal were investigated through changing the SiO 2 /Al 2 O 3 and CaO/SiO 2 ratios, respectively. Results indicate that these two parameters have major effects on partition ratio of boron. A critical oxygen potential value, which yields the highest partition ratio of boron, was calculated as approximately 9 × 10−18 atm. Partition ratio of boron was normalized with oxygen potential at each slag composition in order to isolate the effect of basicity. Borate capacity values were calculated for different slags and it was shown that this parameter is only a function of temperature and slag composition. The kinetics of boron removal was quantified and the total mass transfer coefficient of boron was calculated as 7.48 × 10−6 cm/s. Highlights • A metallurgical method was applied for boron removal from silicon. • A critical oxygen potential, that yields the highest boron removal, was calculated. • Boron distribution was normalized by oxygen potential at each slag composition. • Total mass transfer coefficient of boron was calculated by a kinetic analysis. [ABSTRACT FROM AUTHOR]

This study investigated Fe-17 at% P addition effects on the magnetic properties of Fe-3.5 wt% Si alloys to enhance the electrical resistivity and core loss in powder injection molding. Considering the lowest melting point for 17 at% of P in the Fe-P phase diagram, the effect of P in Fe-3.5 wt% Si was analyzed by adding Fe-17 at% P from 0 to 12 wt% with 4 wt% increments. The feedstocks were prepared based on the processing optimization with respect to the critical solid loading, mixing homogeneity, and binder decomposition. The microstructure; relative density; electrical resistivity; and C, O, N, and S impurities of the sintered alloys were analyzed in correlation with the magnetic properties. The magnetic induction (B 5000 ), maximum permeability, coercivity at 400 Hz and core loss in the frequency range from 50 to 1000 Hz at 1 T were analyzed. The higher magnetic induction and the lower eddy current loss with increasing Fe-17 at% P addition were induced by the higher relative density and electrical resistivity, respectively. [ABSTRACT FROM AUTHOR]

We investigated the ambient temperature structural properties (thickness, width, microstructure, and lattice parameter), and the ambient and high temperature (up to 900 K) direct current (DC) magnetic properties—saturation magnetization ( M S ) and intrinsic coercivity ( H CI )—of rapidly-solidified (melt-spun) Fe- x wt.% Si ( x = 3, 5, & 8) alloys. The wheel surface speeds selected for the study were 30 m/s and 40 m/s. The ribbons produced at the lower wheel surface speed (30 m/s) were continuous having relatively uniform edges compared to the ribbons produced at the higher wheel surface speed. The thickness and the width of the melt-spun ribbons ranged between ∼15 and 60 μm and 500–800 μm, respectively. The x-ray diffraction spectra of the melt-spun ribbons indicated the presence of disordered α -phase, irrespective of the composition, and the wheel surface speed. The lattice parameter decreased gradually as a function of increasing silicon content from ∼0.2862 nm (Fe-3 wt.% Si) to ∼0.2847 nm (Fe-8 wt.% Si). The wheel surface speed showed an insignificant effect on M S while increased silicon content resulted in a decreasing trend in M S . Elevated temperature evaluation of the magnetization ( M - T curves at ∼7.96 kA/m) in the case of Fe-3 & 5 wt.% Si alloy ribbons was distinctly different from that of the Fe-8 wt.% Si alloy ribbons. The curves of the as-prepared Fe-3 wt.% Si and Fe-5 wt.% Si alloy ribbons were irreversible while that of Fe-8 wt.% Si was reversible. The M S for any of the combinations of wheel surface speed and composition decreased monotonically with the increase in temperature (from 300 to 900 K). While H CI increased with the increase in temperature for all the wheel surface speed and composition combination, its nature of increase is distinct for Fe-8 wt.% Si alloy ribbons compared to Fe-3 & 5 wt.% Si alloys ribbons. It appears that rapidly-solidified Fe-3 wt.% Si and Fe-5 wt.% Si alloys ribbons are primarily comprised of the α -phase (disordered phase) while the Fe-8 wt.% Si alloy ribbons are comprised primarily of disordered phase along with minor constituents of an ordered phase. [ABSTRACT FROM AUTHOR]

High saturation magnetic flux density ( B s ) soft magnetic nanocrystalline alloys with good manufacturability were developed in a simple Fe-Si-B-Cu alloy system with high Cu concentrations. The nanocrystalline alloys with high B s of ∼1.77 T and low coercivity of ∼7.1 A/m were obtained by annealing the melt-spun Fe-Si-B-Cu alloys containing 1.7–2.0 at% Cu. The high content of Cu facilitates the formation of high-number-density α-Fe nuclei with an average grain size of ∼6 nm pre-existing in the amorphous matrix, which inhibits the excessive growth of the α-Fe grains by their competitive growth even during the low-heating-rate annealing, resulting in a fine nanostructure and excellent soft magnetic properties. [ABSTRACT FROM AUTHOR]

Semiconducting β-FeSi 2 is a candidate thermoelectric material whose constituents are abundant and eco-friendly, but significant improvements in the relevant properties are needed. This work investigates eutectoid decomposition, α-FeSi 2 → β-FeSi 2 + Si, as a means to modify microstructure and control thermal transport. Process conditions are adjusted to strongly affect both the microstructural lengthscales and morphology, and hence the thermal conductivity. Low temperature annealing of a hypoeutectic sample produces cooperatively-grown Si lamellae, which then decompose into Si nanowires by Rayleigh instability upon further aging. We show that nucleation of eutectoid colonies occurs preferentially on cracks, while at smaller undercooling, nucleation also occurs on eutectic Si particles. The growth velocity, v , and interlamellar spacing, λ , of the pearlitic colonies obey a relation of the type vλ n = f( T ). This sets the bounds of the activation energy for the diffusion mechanism, although the exact mechanism cannot be specified. Nanostructuring of eutectoid Si increases heterointerface density by 40x, with a concomitant reduction in thermal conductivity of 2x. The thermal boundary conductance is determined for the β-FeSi 2 /Si heterointerface, which shows that this interface only weakly scatters phonons. [ABSTRACT FROM AUTHOR]

We have studied Fe 1- x Co x Si (0 ≤ x ≤ 1) crystals using the electrical resistivity ( ρ ), Seebeck coefficient ( S ), and thermal conductivity ( κ ) measurements, to examine the influence of Co substitution on the electrical and thermal transport properties of FeSi. Notably, a metal-insulator transition occurs at x = 0.3 for the Fe 1- x Co x Si series, as the closure of band-gap of FeSi occurs upon Co substitution. Besides, the substituent (Co) induced a significant variation in the Seebeck coefficient, including two sign crossovers. These observations are ascribed to the asymmetric electronic band structure of the Fe 1- x Co x Si compounds. The analysis of thermal conductivity demonstrated that Co substitution has a strong effect on the low-temperature phonon thermal transport of FeSi via boundary scattering and point-defect scattering. Most intriguingly, the substituted end compound CoSi has the largest room temperature thermoelectric figure of merit of about 0.06 which is four orders of magnitude larger than that of undoped FeSi. [ABSTRACT FROM AUTHOR]

The stability, electronic structure, mechanical and thermodynamic properties of Fe 11 Si 5 , Fe 2 Si, Fe 5 Si 3 (with the Mn 5 Si 3 structure), FeSi, α-FeSi 2 and β-FeSi 2 (orthorhombic) were systematically investigated by first-principles calculation. Fe 2 Si, FeSi and β-FeSi 2 are thermodynamically stable intermetallic compounds. The electronic structures and chemical bonding were analyzed by the density of states (DOS) and the electron density distribution map. The stress-strain method was used to calculated elastic constants. The mechanical modulus, such as the bulk modulus (B), shear modulus (G) and Young's modulus (E) were discussed. FeSi has the largest shear modulus and Young's modulus as 188.6 GPa and 457.9 GPa, respectively. The ratio of B/G was used as an indicator for the ductility or brittleness of the compounds. The anisotropic index, three-dimensional (3D) surface contour and planar projections on (001) and (110) planes were used to reveal the anisotropy of Young's modulus. Furthermore, the heat capacity and minimum thermal conductivity were studied. Fe 11 Si 5 has the smallest thermal conductivity with 1.81 W m −1 K −1 . Moreover the temperature-dependent formation enthalpy and entropy were discussed, and the two thermodynamic parameters indicate high temperature decrease the thermodynamic stability of Fe-Si binary compounds. [ABSTRACT FROM AUTHOR]

The size of ε-FeSi phase in iron disilicide with impurities was investigated in this study. The impurity was chosen according to different melting points which are Sn (232 °C), Pb (327 °C), Zn (420 °C), Al (660 °C), Ag (962 °C) and Gd (1341 °C). The mixture of each element was melted in a furnace under Ar atmosphere and the size of ε-phase was analyzed from SEM photographs. It was found that the size of ε-phase has some correlation with the melting point whereby the lower the melting point, the lower the size of ε-phase. The size of a 5%Sn sample was close to that prepared by the thermal quenching method. Data for Sn in the composition of 0.0–1.0% also reveals that the size of ε-phase tends to decrease with increasing Sn composition, up to a factor of 3–4 for 1.0%Sn. This finding could help reduce the annealing time for the peritectoid process (ε + α→β) due to initially smaller ε-phase size. [ABSTRACT FROM AUTHOR]

The orthorhombic (3/2, 2/1) approximant with a = 3.06 nm, b = 1.23 nm, c = 2.24 nm, and the coexisting (2/1, 3/2) approximant of decagonal quasicrystals with a = 1.90 nm, c = 3.64 nm, and β ≅ 90° are found in Al–Cr–Fe–Si alloys by aberration-corrected transmission electron microscope. The structural relationships of these two approximants are analyzed and discussed based on the high-angle annular dark-field scanning transmission electron microscopy images at atomic resolution. We find that both of their structural tiling along the [010] direction can be described by one shield-like tile, with the superiority over the previous HBS tiling model due to the clarity. Combining the shield-like tile and HBS tiling model, the domains of approximants are clearly demonstrated. [ABSTRACT FROM AUTHOR]

This paper reports the preparation of insulated soft magnetic powders by HNO 3 passivation process with SWAP Fe 72.8 Si 11.2 B 10.8 Cr 2.3 C 2.9 amorphous powder. The toroid-shaped cores were fabricated by pressing the mixture of the insulated magnetic powder and silicone resin under a pressure of 1.31 GPa (density = 5.15 g/cm 3 ). The results showed that amorphous magnetic powder produced by 8 vol.% nitric acid insulating process had good frequency characteristics and high quality factor at higher frequency (1 MHz). The value of initial permeability ( μ i ) was 29.03, and the value of quality factor ( Q ) was 68.2. The value of saturation magnetization ( M s ) was 0.93 T, and the coercive force ( H c ) was 89.6 A/m. Furthermore, the amorphous powder was mixed with the Fe–Si–Cr alloy powder by the powder metallurgy process and formed into toroid-shaped cores. The maximum permeability of the toroid-shaped cores with 10 wt.% alloy powder annealed for 10 min at 773 K increased by about 69.8%. The cores were annealed to improve the soft magnetic properties and decrease the stress. The mixed powders also indicated excellent soft magnetic properties; the M s increased from 0.93 T to 0.97 T, and the H c decreased from 89.6 A/m to 68.6 A/m. [ABSTRACT FROM AUTHOR]

Phosphate layers were prepared as the insulation coating for Fe and FeSiAl soft magnetic composites (SMCs) and mechanisms of the phosphating process have been investigated. Effects of high-temperature annealing on the phosphate coating and the magnetic properties of the SMCs have also been revealed. For Fe SMCs, the insulating coating mainly consists of iron phosphate after surface passivation. It degrades into iron phosphide after annealing at relatively high temperatures (600 °C), leading to decreased electrical resistivity and increased eddy current for deteriorated magnetic properties of Fe SMCs. For the FeSiAl SMCs, the phosphate coating mainly contains Al(PO 3 ) 3 , which converts into oxides such as Al 2 O 3 and P 2 O 5 after annealing. These oxides possess high electrical resistivity, and continue to serve as the insulation coating for the composites. Consequently, the resistivity of the FeSiAl SMCs increases with the annealing temperature, which is beneficial to decrease the eddy current loss for enhanced magnetic performance. [ABSTRACT FROM AUTHOR]

A systematic study of the iron–silicon interfaces formed upon preparation of (Fe/Si) multilayers has been performed by combination of modern and powerful techniques. Samples were prepared by thermal evaporation under ultrahigh vacuum onto a Si(1 0 0) substrate. The morphology of these films and their interfaces was studied by a combination of scanning transmission electron microscopy, X-ray reflectivity, angle resolved X-ray photoelectron spectroscopy and hard X-ray photoelectron spectroscopy. The Si-on-Fe interface thickness and roughness were determined to be 1.4(1) nm and 0.6(1) nm, respectively. Moreover, determination of the stable phases formed at both Fe-on-Si and Si-on-Fe interfaces was performed using conversion electron Mössbauer spectroscopy on multilayers with well separated Si-on-Fe and Fe-on-Si interfaces. It is shown that while a fraction of Fe remains as α -Fe, the rest has reacted with Si, forming the paramagnetic c-Fe 1− x Si phase and a ferromagnetic Fe rich silicide (DO 3 type phase). We conclude that the paramagnetic c-Fe 1− x Si silicide sublayer is identical in both Si-on-Fe and Fe-on-Si interfaces, whereas an asymmetry is revealed in the composition of the ferromagnetic silicide sublayer. [ABSTRACT FROM AUTHOR]

Magnetic properties, structure parameters, linear thermal expansion, and Mössbauer effect have been measured on intermetallic compounds La(Fe 0.88 Si x Al 0.12− x ) 13 ( x = 0.033 and 0.096) with the ground ferromagnetic state. The compound with x = 0.033, on growing temperature, demonstrates a transition to antiferromagnetic state at T F – AF ∼ 140 K and then paramagnetic state at T N = 190 K. The compound with x = 0.096 is a ferromagnet with T C = 190 K, and the transition to paramagnetic state is of the first order. The ferromagnetic ordering is accompanied by the lattice expansion by 0.5% and 1.2% for compositions with x = 0.033 and 0.096, respectively. It is established, based on the results of fitting of Mössbauer spectra, that the antiferromagnetic state is predominantly featured by the subspectrum with a positive quadrupole shift, whereas in the ferromagnetic state approximately equal contributions with the quadrupole shifts of different signs are observed. [ABSTRACT FROM AUTHOR]

Distribution coefficient of boron between purified solid silicon and iron–silicon melt at infinite dilution of boron was evaluated to investigate the effectiveness of boron removal from silicon by solvent refining using iron. The estimated values for distribution coefficient of boron at infinite dilution are: 0.49 ± 0.01 (1583 K), 0.41 ± 0.03 (1533 K) and 0.33 ± 0.04 (1483 K). The distribution coefficient increases with temperature showing less boron removal at higher temperatures. The estimated values for self interaction parameter of boron are as follow: −96 ± 12 (1583 K), −111 ± 28 (1533 K) and −159 ± 45 (1483 K). Activity coefficient of boron in solid silicon was obtained and related to temperature as ln γ B in solid Si 0 = ( 16317 ± 282 ) 1 T - ( 7.06 ± 0.18 ) . [ABSTRACT FROM AUTHOR]

Highlights: [•] We analyzed the effect of air annealing on amorphous Fe73.5Si13.5B9M3Cu1 (M=Nb, Mo). [•] We found that Mo alloy was more oxidation resistant than the Nb alloy. [•] Only the air annealed Mo alloy exhibited good magnetic softness. [•] Air annealing would simplify the manufacturing process on Finemet products. [ABSTRACT FROM AUTHOR]

Highlights: [•] Amorphous powder of Fe75Si20B5 (at.%) was prepared by wet mechanical alloying. [•] Spark plasma sintering was used for compaction of amorphous Fe75Si20B5 powder. [•] Increasing SPS time/temperature leads to improvement of AC/DC compacts properties. [Copyright &y& Elsevier]

Flake-shaped particles were fabricated from crushing ingots with ball milling method. Scanning electron microscope (SEM), X-ray diffraction (XRD), vibrating samples magnetometer (VSM) and Mössbauer spectroscopy measurements were carried out to characterize the milled powders. The XRD results show that the DO3 ordered phase coexists with α-Fe(Si,Cr) matrix phase. Generally, grain size decreases with milling time, as internal strain increases. The fitting result of the Mössbauer spectra of the as-prepared powders reveals that the DO3 phase always exists, but the percentage of DO3 phase drops from 52% in the starting powder to 25% after 80h milling. A planar anisotropy of the flake-shaped powders is also demonstrated by the Mössbauer spectra, and found to increase with milling time. The saturation magnetization Ms has a maximum value of 109emu/g after milling of 8h, and then remains at a steady value around 104emu/g. The maximum complex permeability is obtained by 32h milling. [ABSTRACT FROM AUTHOR]

Highlights: [•] Strong temperature dependence of the switching field was observed in FeCrSiB amorphous glass coated microwires. [•] The switching field variation is as high as almost 200% in the temperature range 125–425K. [•] The linearity of the temperature dependence is not influence by the frequency of applied field. [•] Such a behavior gives possibility to employ the FeCrSiB microwires as a very sensitive temperature sensor. [Copyright &y& Elsevier]

Highlights: [•] This paper studies the oxidation of Fe–6at% Si alloy. [•] Oxidation has been done at 570°C in 10−2 mbar for 300h. [•] Silicon has been oxidized from the α-Fe–Si solid solution. [•] Wüstite, magnetite, and fayalite were detected. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic fine particles of metallic Fe coated with graphitic carbon layers were synthesized by annealing Fe2O3 particles with carbon powders at 1673K in nitrogen atmosphere. For comparison, SiC was added to Fe2O3. X-ray diffraction measurement showed that the lattice constants of Fe changed depending on the Si contents. Mössbauer spectroscopy confirmed that Fe–Si alloys were formed by the Si addition and that the iron carbide disappeared. Electron microscope images revealed that the thickness of carbon coating layers increased from 24nm to 36nm as a result of the Si addition. Soaking tests showed that the corrosion resistance of the carbon-coated Fe particles was improved by the addition of Si. The results suggest that Si caused C to leave the Fe cores and move to the surface to form a carbon coating. [ABSTRACT FROM AUTHOR]

Abstract: Iron disilicide synthesis by mechanical alloying was performed. ɛ-FeSi, α-Fe1−x Si2, amorphous FeSi2 were formed with relative intensities depending on the milling period. β-FeSi2 phase was formed after annealing the gridded powder at the temperature where this phase is stable. Mössbauer spectroscopy and X-ray diffraction methods were applied to determine the different phases formed. The morphology of the resulting particles was observed by high resolution scanning electron microscopy. The effect of the milling on bulk iron–silicide samples was and studied chemical effects of the ball milling on Fe–Si2 systems have been studied. [ABSTRACT FROM AUTHOR]

Abstract: Two-side deposition approach was applied to prepare Si-enriched FeSi alloys from 3% Si starting sheets with 0.35mm thickness. FeSi layer was first deposited by direct current (DC) magnetron sputtering on the alloy, which was then subjected to vacuum annealing. It is found that reduction of the deposited FeSi layer thickness suppresses evaporation of Si during the annealing process, which is of great significance in enhancing efficiency of Si penetration into the low-Si starting alloy. After the Si-enriched process, the alloys demonstrate dense and uniform microstructure with 6.5% Si and exhibit α-Fe(Si) bcc structure revealed by X-ray diffractometer (XRD) and transmission electron microscope (TEM). Iron losses of the PVD-prepared Fe–6.5% Si alloy are as low as those of the alloys fabricated by CVD. [Copyright &y& Elsevier]

Abstract: This paper reports the differential scanning calorimetric (DSC) studies of metallic glass ribbon Fe78Si9B13 at different heating rates. It is found that Fe78Si9B13 metallic glass exhibits two-stage crystallization on heating. In order to calculate the activation energies for crystallization various thermal models are employed. The average values of the activation energies (E c) were calculated and found to be 342±10 and 351±8kJ/mol for the first and second phase, respectively. Kinetic parameters such as Avarmi exponent or reaction order (n), dimensionality of growth (m), and frequency factor (K o) are also discussed. The reaction orders obtained for the two stages of crystallization were n 1 =4 and n 2 =5, confirming the bulk crystallizations of the samples. The deduced K o values for the two crystallization peaks are calculated to be 9.8×1018 and 4.6×1018 s−1. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques are used to identify the crystallized phases and morphology of the annealed samples, respectively. Rietveld X-ray profile fittings are also performed that revealed the obtained phases for the Fe78Si9B13 metallic glass were cubic α-Fe(Si) and tetragonal Fe2B with volume fraction of 44% and 56%, respectively. [Copyright &y& Elsevier]

Abstract: A new approach for deposition of in situ nanocrystalline Fe–Si alloy coating on mild steel substrate by mechanical milling has been proposed. The thickness of nanocrystalline coating was a function of milling time and speed. Milling speed of 200rpm was the optimum condition for development of uniform, hard, adherent and dense 200–300μm thick nanocrystalline coating. A possible mechanism, consisting of three steps like repeated impact, cold welding and delamination, has been proposed for the formation of coating. These coatings have resulted in the increase of the hardness to almost double the value before coating. [Copyright &y& Elsevier]

Abstract: The present study examines the effect of solidification rate on the type and morphology of intermetallic compounds (IMCs) of Al-based alloy with high Fe and Si contents in a wide cooling rate range of 1–100K/s. It was found that the final microstructure of Al–14wt.% Fe–2wt.% Si alloy mostly depends upon the solidification rate, which suggests that different solidification rates produced dissimilar microstructures. The increase of cooling rate significantly affects the phase selection sequence, amount and morphology of the IMCs in Al–14wt.% Fe–2wt.% Si. [Copyright &y& Elsevier]

Abstract: Combinatorially sputtered libraries of Fe-rich thin films of the compositions Fe100−x Al x (with 2.9< x <30.9) and Fe100−x Si x (with 2.0< x <22.8) have been prepared and investigated. Compositions have been measured by electron microprobe and crystal structures have been determined by X-ray diffraction. Room temperature 57Fe Mössbauer spectroscopy measurements have been conducted as a function of composition across the libraries. X-ray studies showed all compositions to be of the disordered bcc structure. 57Fe Mössbauer effect center shifts showed trends as a function of composition that were consistent with expectations based on changes in composition and local structure. 57Fe Mössbauer spectroscopy measurements show Fe hyperfine field distributions with a mean Fe field that decreased and a width that increased with decreasing Fe-content. Possible models for atomic order are discussed in the context of the features in the field distribution. For high Al or Si content alloys, the hyperfine field distribution became distinctly bimodal with mean hyperfine field values of the two components that agreed well with expectations for Fe in sites with localized D03 order. Results for Fe–Al and Fe–Si libraries are discussed in terms of literature results for combinatorially sputtered Fe–Ga libraries. [Copyright &y& Elsevier]

Abstract: In this work, the refinement of the Fe94Si6 alloy is achieved by mechanical alloying in a high-energy planetary ball mill under argon atmosphere during various milling times up to 10h. Samples at different milling times were characterized by scanning electron microscope, X-ray diffraction and Mössbauer spectra. After 1h of milling time, it is observed the refinement and coexistence of two phases: the disordered solid solution of type A2 (α-Fe(Si)) and the ordered solid solution of type B2. The relative concentration of the phase B2 varies with milling time, due to the order–disorder transition. The grain size of the phase A2 decreased most gradually up to 10nm with increased milling time. Mössbauer spectra show the presence of a ferromagnetic phase with a mean hyperfine field of 30.1T and a paramagnetic phase with a relative concentration of 6, 5%. [Copyright &y& Elsevier]

Abstract: This paper reports the effects of ternary alloying additions Al, Cu and Nb to Fe75Si25 in high energy ball milling to produce nano-crystalline alloy powder, and its microstructural stability during subsequent high temperature annealing. It is shown that all additions generally retard grain growth up to some temperature. Nb appears to amorphise the alloy. The binary base alloy and Al containing alloy forms the DO3 ordered structure at high temperatures accompanied by rapid grain growth. The Cu and Nb containing alloys precipitate Cu and Nb2Fe at high temperatures but do not become ordered. [Copyright &y& Elsevier]

A decrease of the temperature dependent coercive forces up to around 370 K is discovered in iron silicon alloys, both in quenched samples and in samples which were previously thermally treated to achieve the highest magnetic quality. Alloys of composition Fe-6 wt.% Si and Fe-3 wt.% Si are studied. This reduction in the coercive force is controlled by an increase in the mobility of the domain walls due to the increase in the dislocation's mobility enhanced by the movement of vacancies. It is worthwhile to mention that this reduction in coercive force is only present at these slightly elevated temperatures which are markedly smaller than the usual annealing temperatures for heat treatment of iron silicon alloys while it disappears again at room temperature. Neutron thermodiffraction, magnetic hysteresis loops tracer and mechanical spectroscopy are used as experimental techniques. • Iron silicon alloys, Fe-6.0 wt% Si and Fe-3.1 wt% Si. • Decrease in the value of the coercive force in around 40% which develops up to 370 K. • Mobility of the domain walls controlled by the dislocation's mobility. • Dislocation's mobility enhanced by the movement of vacancies. [ABSTRACT FROM AUTHOR]

Abstract: The deformation behavior of bulk nanocrystalline Fe88Si12 alloy has been investigated with compression tests at different strain rates. The activity volume is 6b 3 which indicates that the deformation mechanism is controlled by the dislocation slip. On the other hand, the critical size of the nanocrystalline Fe88Si12 alloy for deformation mechanism is calculated to be about 5.3nm. It is smaller than the grain size of the nanocrystalline Fe88Si12 alloy (10nm), which also indicates that deformation mechanism of the nanocrystalline Fe88Si12 alloy is controlled by the dislocation pile-up. [ABSTRACT FROM AUTHOR]

By an adequate preparation route, beginning from a Fe 50 Si 50 melted sample, an ordered FeSi simple cubic (sc) phase was obtained. After a milling process the alloy became disordered, its crystallite size decreased and the Fe 3 Si ferromagnetic phase appear and coexist with the FeSi (sc) paramagnetic phase after 24 h milling. All the samples exhibit hysteresis loops with a small coercive field and magnetization values at 2 T. These values increase with milling time; however, a soft magnetic character is exhibited. The small magnetism detected below 24 h milling contrasts with the Mössbauer results for the same samples. This finding is attributed to the grain boundaries and the grain surfaces, in which the coherence is loss and the coordination number of Fe sites changes relative to those inside the grains. These Fe sites can behave ferromagnetically, and act as the nucleation sites for the Fe 3 Si phase. Samples with only the FeSi (sc) phase present a predominant dipolar interaction, between the small magnetic moment of the particles, while those samples with the Fe 3 Si exhibit a predominant ferromagnetic exchange coupling between the Fe 3 Si grains. [ABSTRACT FROM AUTHOR]

Thin films of nominal composition Fe 84.3 Si 4 P 3 B 8 Cu 0.7 have been prepared by sputtering from ribbons of the same alloy. Their microstructure has been studied by means of X-ray diffraction, differential scanning calorimetry and transmission electron microscopy, and reveals a partly amorphous state in the as-prepared samples. Their magnetic properties are soft and comparable to those measured on rapidly quenched ribbons. After annealing in furnace at temperatures up to 400 °C, their soft magnetic properties are improved thanks to the development of a fully nanocrystalline state. Annealing at higher temperature causes the coarsening of the α -Fe like grains, the development of hard magnetic phases and an increase of the coercive field. [ABSTRACT FROM AUTHOR]

In this work we study systematically the influence of mechanical attrition on the magnetic and structural properties of annealed Fe 70 Si 30 alloy by means of Mössbauer spectroscopy, X-ray diffraction measurements and magnetic measurements. In order to obtain different stages of disorder the annealed (ordered) alloys were deformed by ball milling during different number of hours. The annealed alloy presents two different structures (D0 3 and D8 8 ) and the deformation of the annealed sample with ball milling induces the appearance of B20 structure. The variation of the amount of D8 8 and B20 structures makes the Si content of the D0 3 structure vary, which affects the magnetic properties. The disordering process has three different stages, characterized with different magnetic behaviors. [ABSTRACT FROM AUTHOR]

In this paper are presented an analytical and experimental study about the influence of magnetic permeability in phase error of current transformers (CT) with nanocrystalline alloy core. The interest in nanocrystalline alloys in CT cores is based on their magnetic characteristics, e.g., high relative magnetic permeability, low coercive force, and narrow hysteresis loop. To check the influence of the magnetic permeability in the phase error, some experiments were performed such that the only difference in the experimental setup was the ferromagnetic core of the current transformer. In these experiments were investigated four nanocrystalline alloys, with different composition, and a grain-oriented FeSi alloy. From the experimental results obtained, the magnetic characterization of the alloys under test confirmed the premise that the nanocrystalline alloys have superior values of magnetic permeability, lower coercive force and minor hysteresis loops. In tests with CT can be observed that those with nanocrystalline alloy toroidal core presents lower values of phase error in comparison with the CT with FeSi toroidal core, under the same rated conditions. [ABSTRACT FROM AUTHOR]

An inelastic neutron scattering study has been carried out to assess the effects of mechanical milling treatments (10, 20 and 70 h) on an amorphous melt-spun FeSiB ribbon. Faint traces of crystallization were observed after 10 and 20 h milling by X-ray diffraction and Mössbauer spectroscopy and a minor fraction of bcc-Fe was clearly detected after 70 h. Whilst the neutron spectrum S(E) of the 10 h-milled sample, at temperature T = 300 K, does not differ from that of the precursor FeSiB ribbon, the area of the inelastic region of S(E) decreases more and more after 20 and 70 h milling. Moreover, in the samples milled for 20 and 70 h, also the area of the elastic region of the S(E) spectrum is definitely smaller than the one of the FeSiB ribbon. This is consistent with a reduction of the magnetic cross section upon milling and it agrees also with magnetization measurements. We interpret this behavior assuming that the milling treatment causes local alterations of the short-range atomic order within the amorphous phase, and hence of the precursor collinear ferromagnetic order, finally giving rise to a sort of magnetic nanoglass structure. [ABSTRACT FROM AUTHOR]

Deposits of the Fe–6.5wt.%Si alloy rapidly quenched by spray forming were investigated. The order phase can be either B2 or DO3 depending on annealing treatment conditions. The observation of pairs dislocations indicates the presence of super dislocations and B2 antiphase boundaries (APBs) which affects significantly the soft magnetic properties. The dislocations bound the APBS which yield δ fringes when image 200 superlattice reflections. Samples treated at 700°C for 1h were oil quenched, this has induced a decreasing of power loss and the TEM micrographs have showed developed 1/4〈111〉 anti phase domain structure in the B2 phase. The magnetic properties were: power loss of 1.59W/kg and coercive force of 76A/m, at B =1T, f =60Hz. The samples annealed at 1250°C for 1h presented the same interaction between the APBs and magnetic properties presenting better power losses. The magnetic properties were: power loss of 1.30W/kg and coercive force of 40A/m, at B =1T, f =60Hz. This suggests a strong interaction between magnetic properties and anti phase domain structure in the B2 ordered phase. Optical microscopy observations corroborate the magnetic measurement conclusions. [ABSTRACT FROM AUTHOR]

Abstract: The influence of glass incorporation on the microstructure and magnetic properties of Fe-6.5wt% Si alloy processed by metal injection molding (MIM) was investigated. High temperature sintering at 1623K for 2h was performed on the samples with and without the addition of fine glass particles. Microstructural observations revealed that the grain size of the MIM-treated sample without glass particles was approximately one-order higher than the sample with glass particles, which was mainly attributed to the uniform incorporation of glass particles during sintering. Moreover, the size and fraction of the micropores were likely to increase as glass particles were incorporated. At a fixed frequency, the hysteresis loss of the sample without glass particles was slightly lower than that with glass particles while higher loss in the eddy current was obtained in the sample without glass particles than that with glass particles enhancing electrical resistivity. Thus, the total magnetic loss of the MIM-treated Fe-6.5wt% Si alloy decreased significantly due to the incorporation of glass particles. [Copyright &y& Elsevier]

Abstract: Structure changes in Fe75Mo2.5Mn2.5Si6B14 amorphous alloy at heating within temperature range of 293–878K have been studied by means of high-temperature X-ray diffraction method. Intensity curves and main structure parameters estimated from them are analyzed. It is shown that nanocrystallization starts from formation of clusters, size of which as well as a density and volume fraction notably depend on temperature. [Copyright &y& Elsevier]

Abstract: The thermal stability, crystallization behavior, glass-forming ability (GFA), as well as magnetic and mechanical properties of (Fe0.75− x Tb x B0.2Si0.05)96Nb4 (x =0.01–0.07) bulk metallic glasses (BMGs) with Tb addition were investigated. With the increase of Tb content, the glass transition temperature (Tg ) and the crystallization temperature (Tx ) shifted towards higher temperature. The supercooled liquid region (ΔTx = Tx − Tg ) increased from 46 to 100K for alloy with x =0.04, due to the tendency to form Fe23B6 phase and local chemical short-range ordering. Besides, the x =0.04 alloy decreased the liquidus temperature (Tl ) and approached alloy to a eutectic point, leading to the best GFA with a diameter of 3.5mm. The BMGs exhibited high compressive fracture strength of 3300–4000MPa and high Vickers hardness of 1020–1110, combined with good soft-magnetic properties, i.e., high saturation magnetic flux density of 0.52–1.14T, coercive force as low as 2.5A/m. The mechanisms for high GFA and characteristic exothermic event in the supercooled liquid for the (Fe0.75− x Tb x B0.2Si0.05)96Nb4 BMGs were discussed. [Copyright &y& Elsevier]

Highlights: [•] Onset of devitrification of amorphous FeSiPB alloys was studied by TEM and XRD. [•] Primary phase of β-Mn structure type precipitates in alloys with 3–5at.% P. [•] The phase is formed by nearly polymorphous transformation. [•] Small alloying additions change the type of the primary phase. [•] Knowledge of primary phases helps to understand structure of amorphous phase. [ABSTRACT FROM AUTHOR]

Abstract: Fe–Si alloys are widely used for magnetic applications. However, it is very difficult to process Fe–Si with a silicon content exceeding 3.5wt.%Si (upper limit for products commercially available by the I/M route) due to the alloy''s low ductility, which is attributed mainly to the formation of B2 and DO3 ordered phases that embrittle the material. To overcome this obstacle, the main focus of this work was to produce thin sheets of Fe–5wt.%Si alloy in two steps: (1) as a Fe–3.5%Si+3%Sip (Si particles) composite, using spray forming, and (2) rolling and heat treating (HT) the composite to dissolve the silicon and homogenize its content throughout the thickness of the sheet. To this end, 3wt.%Sip were co-injected into the main stream of the Fe–3.5wt.%Si spray, followed by hot-rolling of the billet at 850°C to obtain 0.45mm gauge thin sheets. The final material was heat-treated at 780/510°C for 8h or at 1250°C for 1h and then air cooled. The grain orientation was analyzed by EBSD and the distribution of iron, silicon and impurities was identified by X-ray dot mapping. The heat treatment caused diffusion and dissolution of the silicon particles and grain growth. However, the final silicon content was strongly dependent on the atmosphere of the heat treatment furnace. In the absence of oxygen, the silicon content reached 4.9wt.% distributed homogeneously throughout the thickness of the composite. In the presence of oxygen, the silicon diffused to the surface and only 3.5wt.% remained in the matrix. [Copyright &y& Elsevier]

Abstract: Fe–Si alloys have excellent soft magnetic properties, especially around 12at.% Si. However, their industrial applications are limited because they lack the ductility required in rolling operations for the fabrication of thin sheets, thus leading to cracking. The brittleness of high silicon alloys is caused by order–disorder reactions at low temperatures. This work involved an analysis of the effect of heat treatment on the crystalline structure of thin sheets of Fe–5wt%Si alloy obtained in a two-step fabrication route: (1) spray forming of Fe–3.5%Si+2.0%Sip composite and (2) rolling and heat treatment of the composite to dissolve the silicon and homogenize its content across the thickness of sheet samples. Structural and microstructural analyses indicated the success in fabricating thin sheets of Fe–5wt%Si alloys with such strategy. The presence of the ordered B2 phase had an important effect on the texture development and therefore on the magnetic properties of these alloys. [Copyright &y& Elsevier]

Abstract: Suction cast technique is employed for producing Fe–6.5wt.% Si alloy, which is very brittle at room temperature due to the appearance of ordered phases. The master alloy was melted and then rapidly quenched into a set of copper molds to form rod or sheet. Microstructure, micro-hardness and X-ray diffraction analyses were carried out to investigate its unique properties in comparison with conventionally cast method. The rapidly quenched sheets were cold rolled to investigate the quenching effect on its rolling workability. Rapid quenching combined with cold rolling with a large reduction ratio is effective to produce cold rolled Fe–6.5wt.% Si alloy sheet. [ABSTRACT FROM AUTHOR]