Formation and physical properties of Fe-based bulk metallic glasses with Ni addition

Purpose: The main aim of the paper was investigations of formation and changes of physical properties (magnetic properties and microhardness) of Fe based bulk metallic glasses (BMGs) with Ni addition. Design/methodology/approach: The following experimental techniques were used: transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) phase analysis method to test the structure, electrical resistivity in situ measurements (four-point probe), measurements of magnetic properties, microhardness of investigated ribbons was determined by Vickers method. Findings: The structural studies revealed an amorphous structure for the ribbons with thicknesses up to 0.27 mm, regardless of their thickness. Research limitations/implications: More investigations for example Mössbauer spectrometry have to be conducted on different thickness of ribbons in order to confirm conclusions contained in the work. Practical implications: According to the results presented in the present paper the examined Fe-based bulk glassy alloys with Ni addition as a soft ferromagnetic material may be utilized in construction of magnetic cores such as choke coils, common mode and noise filter and is of great technological interest. Originality/value: The originality of the paper are examinations of changes of structure and physical properties on cross section and on surface of ribbons

Magnetic relaxation in iron based melt spun ribbons

In this paper magnetic relaxation processes in iron based amorphous alloys are examined in order to determine thermal/time instability of magnetic properties at room temperature. It was shown that the reversible component of magnetic relaxation in Fe74Cu1Cr3Si13B9 alloy can be well described by the coupling model usable for diffusion in strongly correlated systems. The proposed approach allows monitoring initial stages of structural relaxation

Magnetoimpedance effect in amorphous and nanocrystalline alloys based on iron

Purpose: The main purpose of the paper is to study magnetic, electrical and plastic properties of the selected group of amorphous alloys in the context of their application as magnetoimpedance sensors. Design/methodology/approach: The presented results were obtained by applying different magnetic methods (low field permeability measurements, magnetic relaxation, magnetization versus magnetic field, magnetization in saturation versus temperature, magnetoimpedance effect versus static magnetic field and/or frequency), resistivity versus temperature and Young’s modulus versus temperatures. Structural changes taking place in annealed samples were examined by making use of X-ray diffraction method and high resolution electron microscopy observations. Findings: It was shown that in all examined amorphous alloys soft magnetic properties can be enhanced by applying a suitable 1-h annealing at temperatures Top listed in Table 1. After annealing at this characteristic temperature magnetic permeability in relation to the as quenched state increases more than 20 times and non-contact magnetoimpedance effect (ΔZ/Z)ncmax is of the order of 104%. This effect can be explained based on the random anisotropy model supplemented by energy terms describing magnetoelastic energy and stabilization energy related to free volume content. For the alloys for which the optimized microstructure corresponds to the relaxed amorphous phase the plastic deformation corresponding to formation of brittle cracks is much higher than for the examined nanostructured alloys. In the frequency range from 700 kHz to 2 MHz magnetoimpedenace effect (ΔZ/Z)ncmax is approximately constant. Research limitations/implications: Searching of new soft magnetic materials in the group of amorphous alloys based on iron obtained by melt spinning can give a promising result. For example one can obtain very good soft magnets showing also good mechanical properties. Practical implications: Based on the presented results one can obtain very good soft magnetic material with low field relative magnetic permeability of about 16 000 (Fe74Cu1Zr3Si13B9). In the examined group of amorphous alloys the best candidate for magnetoimpedane sensor applications is the Fe75,75Ag0,25Nb2B22 alloy for which (ΔZ/Z)ncmax = 104% and plastic deformation εop=0.015. Silver as an alloying addition to the base Fe-Nb-B alloy significantly improves the alloy plasticity. Originality/value: It was shown that the examined amorphous alloys based on iron after applying a suitable thermal annealing can be used as promising materials for nagnetoimpedance sensors

Thermal stability, crystallization and magnetic properties of Fe-Co-based metallic glasses

The aim of the paper was to investigate thermal stability, crystallization and magnetic properties of Fe-Cobased metallic glasses (MGs). Investigations were carried out on amorphous ribbons with the compositions of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 and [(Fe0.6Co0.3Ni0.1)0.75 B0.2Si 0.05]96Nb4. Thermal properties (liquidus Tl and melting Tm temperatures) of the pre-alloyed ingots upon heating and cooling were analyzed by DTA at a heating/ cooling rate of 0.33 K s-1 under the purified argon atmosphere. The structure of the ribbons was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) method. Kinetics of the crystallization process was examined by applying differential scanning calorimetry (DSC) method, and experiments performed in thermal analysis involve heating at a constant rates b = 0.17, 0.33 and 0.5 K s-1. Additionally, the conventional crystallization temperature Tx was determined from the normalized isochronal resistivity curves a(T) with heating rate 0.0083 K s-1. a is the temperature coefficient of resistance and a = q-1 dq/dT. The Tx, can be obtained from the condition a = 0 (Stokłosa et al. in J Alloy Compd 509(37):9050–9054, 2011). The saturation magnetization M(T) was measured in situ with heating rates 0.083 K s-1 using magnetic balance (Szewieczek and Lesz in J Mater Process Tech 162–163:254–259, 2005)

Analysis of the nanocrystalline phase formation process in amorphous Fe-X-Si-B alloys

The process of nanocrystalline phase formation, affecting magnetic properties, in amorphous Fe78Si8 Bι4, Fe76 ΑI2 Si8 Β14 , Fe76 Cr2 Si8 B14 and Fe76 Mo2 Si8 B14 alloys has been studied in the paper. Investigations have been carried out using the electrical resistivity method, magnetic methods, transmission electron microscopy and X-ray diffraction. A nanocrystalline phase in the amorphous matrix has been obtained by isochronous or isothermal vacuum annealing. Phase composition of samples has been determined directly after manufacturing and after crystallization annealing on the basis of X-ray diffraction and electron diffraction. Transmission electron microscopy was used to determine phase morphology, dimensions of formed nanocrystalline phase and transition phase. Alloying elements have been found to affect changes of magnetic properties in amorphous and nanocrystalline states. For Fe76Mo2 Si8 Β14 alloys a significant increase in crystallization temperature, making difficult nanocrystalline phase growth and increase in thermal stability of magnetic permeability have been observed

Assessment of heavy metal pollution in Vistula river (Poland) sediments by using magnetic methods

The present study evaluated the level of heavy metal (HM) pollution in Vistula river sediments in a highly urbanized Warsaw agglomeration (Poland). Magnetometry was used to assess the pollution level by measuring the fine fractions (0.071 mm and <0.071 mm) of sediments collected from the surface layer of the riverbank. The magnetic methods (e.g., mass magnetic susceptibility χ, temperature-dependence magnetic susceptibility, and hysteresis loop parameters) were supplemented by microscopy observations and chemical element analyses. The results showed the local impact of Warsaw’s activity on the level of HM pollution, indicated by the maximum concentrations of magnetic particles and HM in the city center. The sediment fraction <0.071 mm was dominated by magnetite and by a large amount of spherical-shaped anthropogenic magnetic particles. The pollution from the center of Warsaw was transported down-river over a relatively short distance of approximately 11 km. There was a gradual decrease in the concentrations of magnetic particles and HM in areas located to the north of the city center (down-river); furthermore, χ and concentrations of HM did not decrease to the values observed for the area to the south of Warsaw (up-river). The study showed two possible sources of sediment pollution: traffic-related and heat and power plant emissions. The influence of an additional source of pollution cannot be excluded as the amount of spherules in the sediments at the center was extremely high. The present study demonstrates that magnetometry has a practical application in detecting and mapping HM pollution in river systems

Structural relaxation in Fe78Nb2B20 amorphous alloy studied by Mossbauer Spectroscopy

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

Magnetic and mechanical properties in FeXSiB (X=Cu, Zr, Co) amorphous alloys

Purpose: The idea of the paper is to study the influence of different alloying additions (Cu, Zr, Nb) on structural relaxation, crystallization, and improvement of soft magnetic properties in amorphous alloys of the type FeXSiB obtained by melt spinning technique. Design/methodology/approach: Magnetic and electric characteristics of the as quenched and successively annealed samples were determined at room temperature. Experiments were carried out by applying magnetic permeability measurements (Maxwell-Wien bridge), magnetic after effects, resistivity (four points probe), magnetostriction coefficient (infrared optical sensor) and magnetization (magnetic balance and fluxmeter). Findings: It was shown that soft magnetic properties of the examined alloys can be optimized by applying 1-h annealing at a specific temperature. The process of the improvement of soft magnetic properties is found to be diffusion controlled. The Arrhenius parameters of this process were determined by applying magnetic measurements. 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, electric and electromagnetic fields 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 improvement of soft magnetic properties effect as a diffusion-controlled process. The influence of different alloying additions on the course of this process is well established

Magnetic properties of Fe76X2Si8B14 (X= Al, Cr, Mo) amorphous alloys

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