Some selected properties (magnetic, plastic, elastic) in amorphous Fe76-xAgxNb2Si13B9 (x = 0.5, 0.75, 1.0) alloys, obtained by melt spinning technique, are presented and discussed in detail. It was shown that a suitable heat treatment of the as quenched samples (i.e. the optimization annealing) leads to a significant improvement of soft magnetic properties (permeability increases at least 10 times). The observed effect is attributed to formation of the so-called relaxed amorphous phase free of iron nanograins. Special attention is paid for loss separation into different components: hysteresis loss, eddy-current loss and residual loss. The latter effect can be attributed to diffusion of free volume and practically disappear after the optimization annealing. (c) 2015 Elsevier B.V. All rights reserved.

It was shown that soft magnetic properties of Fe78Nb2B20 amorphous alloy can be significantly improved by applying 1-h annealing at temperature 623 K (permeability increases even about 8 times). The Mössbauer Spectroscopy technique indicated that the optimized microstructure (corresponding to the maximum magnetic permeability) is free of iron nanograins and should be attributed to annealing out of free volume and a reduction of internal stresses i.e. to the relaxed amorphous phase.

Influence of 1 h annealing in vacuum on magnetic, electrical and plastic properties of Fe76Nb2Si13B9, Fe75Ag1Nb2Si13B9 and Fe75Cu1Nb2Si13B9 melt spun ribbons were carefully investigated. It was shown that in all cases soft magnetic properties can be significantly enhanced by applying 1-h annealing at characteristic temperatures T-op. This optimization annealing causes that permeability increases more than 15-times and magnetic losses (tangent of loss angle) achieves a minimum in relation to the as quenched state. Using structural examinations (X-ray and HRTEM) it was shown that for the Fe75Cu1Nb2Si13B9 alloy the optimized microstructure corresponds to a nanocrystalline alpha Fe(Si) phase whereas in other alloys to a relaxed amorphous phase free of iron nanograins. As a consequence of this fact the Fe76Nb2Si13B9 and Fe75Ag1Nb2Si13B9 alloys show higher plasticity in comparison to the nanocrystalline Fe75Cu1Nb2Si13B9 alloy. Temperatures of the first stage of crystallization, and related diffusion parameters were determined using measurements of resistivity versus temperature with different heating rates. (C) 2011 Elsevier B. V. All rights reserved.

In the paper Fe82Nb2B16, Fe80Nb2B18 and Fe78Nb2B20 amorphous alloys, obtained by melt spinning, were examined. It was shown that the alloys studied in the as quenched state and in the relaxed amorphous state or in nanocrystalline state (after a suitable annealing) belong to very good soft magnetic materials with relatively high resistivity. The influence of annealing on brittleness as well as magnetic and electric properties measured at room temperature was examined. A correlation between sample microstructure (in the as quenched state and after annealing) and different physical properties is discussed. It was shown that the observed changes of relative magnetic permeability can be explained by changes of magnetoelastic energy, concentration of microvoids frozen during production process, effective anisotropy constant and magnetic polarisation.

In this paper, the influence of structural relaxation on magnetoelastic coupling in iron-based amorphous alloys is carefully examined. In order to change free volume content, the as-quenched samples were annealed for 1 h at temperatures corresponding to the structural relaxation. Magnetostriction measurements were carried out at room temperature using the infrared magnetodilatometer. It was shown that both the parallel magnetostriction coefficient λ∥ and the perpendicular magnetostriction coefficient λ⊥ decrease with decreasing free volume content, whereas the saturation magnetostriction λS (proportional to λ∥−λ⊥) remains constant. In contrast, the volume magnetostriction ω strongly depends on free volume content and follows the relation ω∝ m 2 (where m is the reduced magnetization). Moreover, it was confirmed that λS can be attributed to one-ion spin correlations, short range in nature.

The influence of boron on crystallization and magnetic properties of the Fe(98-x)Nb(2)B(x),, (x = 11, 14, 16, 18, 20, 22) group of alloys obtained by melt spinning method were investigated. Relative magnetic permeability (mu(r)), parallel magnetostriction coefficient in saturated magnetic field (lambda(parallel to s)) and resistivity (rho) were determined for samples in the as quenched state and after 1h annealing in the vacuum. It was found that the characteristic temperatures, that is the Curie temperature (T(c)), the temperature of the first stage of crystallization (T(x1)), and the 1-h temperature of soft magnetic properties optimization. annealing (T(op)) increase with increasing boron content in the examined alloys. The observed increase of the Curie temperatures is explained based on the molecular field approach Mechanism of the increase of the characteristic temperatures T(x1) and T(op) with increasing B content is discussed in terms: of the diffusion model. Activation energies (E(x1))of the first stage of crystallization were determined. Microstructures of samples in the as quenched state and after annealing were examined by X-ray diffraction and high resolution electron microscopy methods. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The aim of the present paper is to find correlations between structural changes and electrical, mechanical and magnetic properties in Fe78Si13B9, Fe76Nb2Si13B9, Fe75Cu1Nb2Si13B9, Fe75Cu1Zr1Co1Si13B9, amorphous and nanocrystalline alloys obtained by melt spinning technique. The influence of annealing on material brittleness, magnetic and electric properties was examined. It was found that the optimization of soft magnetic properties effect is a thermally activated process and its diffusion parameters were determined. It was shown that for the alloys containing Cu, Nb and Zr as alloying additions, the optimization process can be attributed to formation of a nanocrystalline phase. In contrast to this for the FeSiB and FeNbSiB alloys the optimization process should be related to the relaxed amorphous phase.

In the present paper the influence of 1-h annealing (temperature range from 300 to 800 K) on magnetic, plastic and electrical properties of the Fe(75.75)Ag(0.25)Nb(2)Si(13)B(9), Be(75.75)AB(0.25)Nb(2)B(22), Be(74.75)AB(0.25)CO(5)Nb(2)B(18) amorphous alloys were carefully examined. For all the tested alloys the enhancement of magnetic permeability effect was observed i.e. initial magnetic permeability measured at room temperature for annealed samples shows a sharp maximum. A possible mechanism explaining this effect is discussed in detail. Moreover it was found that at room temperature plastic deformation of the annealed samples depends on the progress of structural relaxation (free volume content). Activation energies and preexponential factors of the first stage of crystallization process were determined from the isochronal resistivity curves measured with different heating rates (Kissinger method). The Curie temperatures from the magnetization curves versus temperature were also determined. (C) 2010 Elsevier B.V. All rights reserved.

In the present work X-ray studies were performed on annealed Fe78Nb2B20 amorphous alloy prepared by melt-spinning technique. All the samples were annealed in vacuum for 1 hour at temperatures up to 800°C. For the studied alloy -Fe and Fe2B are the stable, crystalline phases. The -Fe crystallized as the first crystalline phase in the sample annealed at 350°C. On the other hand, metastable Fe3B phase appeared to be stable during annealing in 425-800°C temperature range. The best fitting of the experimental X-ray data to as jet available ICDD files was obtained for Ni3P type structure (39-1315 – S.G.: I (82)). New, experimental powder diffraction data for metastable Fe3B phase prepared according to ICDD standards were elaborated for the sample annealed at 600°C. For this sample the best agreement between the calculated values of lattice constants and positions of experimental diffraction lines was obtained. The X-ray data were collected using X-Pert Philips diffractometer equipped with curved graphite monochromator on diffracted beam. The Treor program was applied for the analysis of X-ray diffraction data.

Curing process of an amine-epoxy system was investigated using vibrating reed technique and torsion pendulum apparatus, working at frequencies of about 100Hz and 1Hz, respectively. The measurements of mechanical spectra were carried out in isothermal conditions (300–325K) at different frequencies in time domain i.e. in the course of chemical reaction between epoxy resin and a hardener. It was shown that the curing reaction is observed as an asymmetrical maximum of Q−1(t) which position is correlated with the inflection point of free vibrations frequency f(t) curve. An increase of the measurement temperature and frequency causes a shift of the observed mechanical spectra into shorter times.

In the present work elastic properties of the epoxy system coatings deposited on aluminum-based alloy substrate were investigated using internal friction methods i.e. i) vibrating reed technique (frequency about 100Hz) and ii) torsion pendulum (1Hz). The apparent Young's modulus γ2E (γ — adhesion coefficient, E — Young's modulus of the coating) was determined for different state of substrate surface and curing temperatures. It was shown that γ2E correlates linearly with the bond shear strength obtained from tensile tests by applying Instron machine (destructive method). Moreover, the dependence γ2E versus curing temperature shows a maximum at 350K. Isothermal measurements of mechanical loss tangent Q−1(t) versus curing time show that the curing reaction of the epoxy material is observed as an asymmetric peak whose position shifts towards shorter times with increasing curing temperatures. Activation energy of the curing process determined from this shift is found to be Ea=(51±3) kJ/mol.

Application of the Fe80Nb6B14 amorphous alloy to electromagnetic shielding was examined in detail using different experimental techniques. For shields made of the optimized (annealing at 700 K/1 h) amorphous ribbons the shielding effectiveness b was measured versus frequency f and shield thickness h. it was shown that for h = 200 mu m in the frequency range 2 MHz < f < 15 MHz (the near-zone, electric field) b decreases from 55 dB to 20 dB, In the frequency range 0.2 kHz < f < 10 kHz (the near-zone, magnetic field) b > 20 dB. The best shielding effectiveness, i.e. b > 100 dB was obtained for electromagnetic field in the frequency range 200 MHz < f < 1000 MHz (the far-zone). (c) 2008 Elsevier B.V All rights reserved.

Purpose: The idea of the paper is to study the influence of thermal annealing and alloying additions on magnetic properties, optimization and crystallization processes in Fe76X2Si8B14 (X=Al, Cr, Mo) amorphous alloys. Design/methodology/approach: For annealed samples (1 h, Ta ranging from 300 K to 800 K) at room temperature magnetic permeability was measured by applying Maxwell-Wien bridge (frequency about 1030 Hz and magnetic field H=0.5 A/m). Magnetostriction coefficients – parallel and perpendicular were determined by applying infra-red magneto-dilatometer. Magnetization in saturation versus temperature was measured by making use of magnetic balance (field 0.5 T). Findings: It was shown that alloying additions in the examined alloys cause a decrease of the Curie temperature, an increase of magnetic permeability and magnetization in saturation. The observed ESMP (enhancement of soft magnetic properties) effect in the examined alloys can be attributed to the so-called relaxed amorphous phase free iron nanograins. It was shown that parallel and perpendicular magnetostriction coefficients depend on annealing temperatures which means that these quantities are sensitive on free volume content. Research limitations/implications: The obtained results are a part of a broad area of examinations devoted to establishing of the influence of different alloying additions and thermal annealing on soft magnetic properties of amorphous alloys obtained by melt spinning technique. Practical implications: The examined alloys belong to a modern group of soft magnetic materials, which can be used as core transformers, magnetic sensors, shields of magnetic etc. The obtained results may be used for preparing soft magnetic ribbons for specific applications. Originality/value: The originality of the paper lies in examination of the influence of free volume content on magnetostriction coefficients.

In the present paper, the influence of Nb and Cr on intensity of structural relaxation, crystallization processes, electric and magnetic properties in the Fe76Nb2Si13B9, Fe76Cr2Si13B9 and Fe76Nb1Cr1Si13B9 alloys were investigated. It was shown that the improvement of magnetic permeability caused by a suitable annealing is a thermally activated process. Activation energy of this process is found to be of the order of 1eV. Cr as an alloying addition to the Fe–Si–B alloy does not change the 1h optimization annealing temperature and causes an increase of its efficiency. Nb as an alloying addition causes an increase of the 1h optimization annealing temperature, and also the temperature of the first step of crystallization.

In the present paper long-term stability of magnetic properties of different amorphous and nanocrystalline alloys was studied. Magnetic properties were measured for annealed samples (300 < Ta < 900 K) directly after annealing and after long-term aging at room temperature. It was shown that for the Fe(75.3)Cu(1)Zr(1.7)Si(13)B(9) alloy magnetic permeability of the optimized samples is stable during 8 years aging. For Fe(86-x)Nb(x)B(14) alloys the observed long-term instability (3 years aging) is due to annealing out of free volume leading to formations of small iron clusters coherent with the amorphous surroundings. (C) 2008 Elsevier B.V. All rights reserved.

The present paper focuses on the influence of alloying additions on magnetostriction coefficient, concentration of free volume and magnetization in Fe–X–Si–B, and Fe–X–Cu–Si–B amorphous alloys. It was shown that in one group of alloys, the enhancement of soft magnetic properties effect can be attributed to formation of nanocrystalline phase αFe(Si), a decrease of the magnetostriction coefficient and annealing out of free volume. In the second group of alloys, this effect is due to a decrease of the magnetostriction coefficient and annealing out of free volume i.e. takes place in the relaxed amorphous phase.

The crystallization and optimization of magnetic properties effects in FeXSiB (X=Cu, V, Co, Zr, Nb) amorphous alloys were studied by applying X-ray diffraction methods, high resolution transmission electron microscopy (HRTEM), resistometric and magnetic measurements. The temperatures of the first and the second stage of crystallization, the 1h optimization annealing temperature and the Curie temperature were determined for different amorphous alloys. Activation energies of crystallization process were obtained by applying the Kissinger method. The influence of alloy additions on optimization effect and crystallization processes was carefully examined.