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1

Magnetoimpedance effect in amorphous and nanocrystalline alloys based on iron

Kwapuliński P.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 47, nr 2

166--176

EN

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 noncontact 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.

2

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

Lesz S., Kwapuliński P., Nowosielski R.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 1

35-40

EN

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.

3

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

Madej Ł., Stokłosa Z., Chrobak A., Kwapuliński P., Rasek J., Haneczok G.

Archives of Materials Science and Engineering

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2008

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Vol. 34, nr 1

9-13

EN

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.

4

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

Kwapuliński P., Rasek J., Stokłosa Z., Badura G., Kostrubiec B., Haneczok G.

Archives of Materials Science and Engineering

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2008

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Vol. 31, nr 1

25-28

EN

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.

5

Phse stability and structural relaxation in Fe-Nb-B amorphous alloys

Chrobak A., Kubisztal M., Chrobak D., Kwapuliński P., Stokłosa Z., Rasek J.

Archives of Metallurgy and Materials

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2006

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Vol. 51, iss. 4

561-564

EN

In the present paper the phase stability in the Fe86-xNbxB14 (26x68) group of amorphous alloys was examined by applying i) DSC measurements, ii) Young modulus versus temperature and iii) magnetic after effects. It was shown that different physical quantities i.e. i) the optimized magnetic permeability, ii) the heat of amorphous – crystalline transition and iii) the change of Young modulus taking place during structural relaxation of amorphous Fe-Nb-B alloys exhibit the remarkable maximum for x = 6 at.% Nb. The degree of amorphisation measured by the heat transition (energetic difference between amorphous and crystalline state) or by change of the Young modulus (intensity of structural relaxation) is the main reason of structural changes favorable for soft magnetic properties enhancement effect. Intensity of magnetic after effects, corresponding to the free volume content, decreases with increasing Nb content.

PL

W niniejszej pracy badano stabilność fazową w amorficznych stopach Fe86-xNbxB14 (26x68) poprzez zastosowanie takich technik pomiarowych jak pomiary kalorymetryczne DSC, pomiary modułu Younga w funkcji temperatury oraz pomiary przenikalności magnetycznej po rozmagnesowaniu próbki. Z otrzymanych wyników wynika, że różne wielkości fizyczne (zoptymalizowana przenikalność magnetyczna, ciepło krystalizacji, zmiana modułu Younga w trakcie relaksacji strukturalnej) wykazują charakterystyczne maksimum dla próbek o zawartości x = 6% Nb. Na tej podstawie sformułowano wniosek, że stopień amorficzności badanych stopów, mierzony jako ciepło przemiany ze stanu amorficznego do krystalicznego (energia swobodna zamrożona procesie produkcji próbek) oraz zmiana modułu Younga (natężenie relaksacji strukturalnej), jest decydującym czynnikiem dla korzystnych, z punktu widzenia optymalizacji miekkich własciwości magnetycznych, przemian strukturalnych. Zmiana przenikalności magnetycznej po rozmagnesowaniu, odpowiadająca stężeniu mikropustek w strukturze amorficznej, maleje wraz ze wzrostem stężenia niobu.

6

Influence of Cu and Zr on crystallization and the optimization of magnetic properties in amorphous alloys based on iron.

Stokłosa Z., Rasek J., Kwapuliński P., Badura G., Haneczok G.

Archives of Materials Science

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2004

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Vol. 25, nr 4

477-483

EN

In the present paper the fluence of Cu and Zr as alloying addictions to the Fe78Si13B9 base alloy was examined in detail. It was shown that Cu causes an increase of magnetic relaxation intensity, accelerates diffusion processes and separates the first and second stages of crystallization. Zr atoms cause a slowing down of diffusion processes, a decrease of magnetic relaxation intensity and an improvement of soft magnetic properties of the examined material.

7

Application of soft magnetic amorphous materials as magnetic shields.

Kwapuliński P., Chrobak A., Haneczok G., Stokłosa Z., Rasek J.

Archives of Materials Science

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2004

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Vol. 25, nr 4

455-460

EN

The Fe80Nb6B14, Fe76Nb2B22 and Fe76Zr2B22 amorphous alloys were tested for application as magnetic shields. It was shown that initial magnetic permeability of ribbons of the Fe80Nb6B14 alloy after annealing at 700 K/1-h is of the order of 10 to 4. The shielding effectiveness b for this alloy strongly depends on shield thickness h and magnetic field intensity. For h=200 microm b>20 dB up to 4x10 to 3 A/m.

8

Właściwości magnetyczne stopów typu nanoperm oraz ich wykorzystanie na ekrany pola elektromagnetycznego.

Haneczok G., Kwapuliński P., Stokłosa Z., Rasek J., Wroczyński R.

Archiwum Nauki o Materiałach

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2003

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T. 24, nr 4

373-391

PL

W pracy pokazano, że miękkie właściwości magnetyczne amorficznych stopów Fe76X2B22 (X=Cr, Zr, Nb) oraz Fe87Nb2B11 i Fe78B22 mogą być znacznie polepszone przez zastosowanie jednogodzinnego wygrzewania optymalizującego w temperaturach zbliżonych do temperatury krystalizacji. Pokazano, że dodatki stopowe Zr i Nb opóźniają procesy dyfuzyjne zachodzące w materiale i przesuwają pierwsze stadium krystalizacji (nanokrystalizacji) do wyższych temperatur. Obniżenie stężenia boru w stopach z dodatkiem Nb z 22 %at. do 11 %at. prowadzi do obniżenia temperatury wygrzewania optymalizującego o 150 K i obniżeniem temperatury Curie fazy amorficznej o 130 K. Z grupy badanych materiałów najlepszym stopem na ekrany tłumiące pole elektromagnetyczne okazał się stop Fe87Nb2B11. Pokazano, że w tym przypadku tłumienie fali elektromagnetycznej dla częstotliwości 0,2-1 GHz zawiera się w przedziale 30-55 dB.

EN

It was shown that soft magnetic properties of amorphous Fe76X2B22 (X=Cr, Zr, Nb), Fe87Nb2B11, and Fe78B22 alloys can be significantly improved by 1-h thermal annealing at temperatures closed to the crystallisation temperature. Alloying additions of Zr and Nb cause a slowing down of diffusion processes and a shift of the crystallisation temperature as well as the optimisation annealing temperature into high temperature region. A reduction of boron content for alloys with Nb (from 22 at.% to 11 at.%) causes a decrease of the 1h optimisation annealing temperature of about 150 K and the Courie temperature of the amorphous phase of about 130 K. Application of the examined materials as electromagnetic shields shows that the best parameters were obtained for the Fe87Nb2B11 alloy. In this case in the frequency range 0.2-1 GHz damping varies from 30 to 55 dB.

9

Krystalizacja stopów amorficznych typu Fe-X-Si-B (X=Cr, Mo)

Lelątko J., Pająk L., Rasek J., Kwapuliński P., Stokłosa Z.

Archiwum Nauki o Materiałach

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1998

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t. 19, nr 4

255-267

PL

Z danych literaturowych oraz wcześniejszych badań własnych autorów wynika, że właściwości fizyczne, a w szczególności właściwości magnetyczne i elektryczne amorficznych stopów Fe-X-Si-B, otrzymanych metodą melt spinning, bardzo silnie zależą od rodzaju dodatku stopowego X. Dalszą modyfikację tych właściwości można uzyskać w wyniku odpowiedniej obróbki cieplnej. W niniejszym artykule przedstawiono wyniki badań wpływu wygrzewania w zakresie temperatur 300-875 K na strukturę oraz właściwości elektryczne stopów Fe78Si8B14, Fe76Mo2Si8B14 i Fe76Cr2Si8B14. Na podstawie badań strukturalnych i rezystometrycznych stwierdzono, że dodanie do stopu Fe78Si8B14 molibdenu lub chromu powoduje spowolnienie rozrostu fazy alpha-Fe(Si) w osnowie amorficznej. Określono sposób zarodkowania, morfologię tworzących się faz oraz przeprowadzono ich identyfikację. Stwierdzono duży wpływ molibdenu na rozdrobnienie ziarn. Otrzymane wyniki badań strukturalnych pozwoliły na wytłumaczenie obserwowanych zmian właściwości fizycznych badanych stopów, występujących wraz ze wzrostem temperatury.

EN

From literature data and from the results of authors' previous investigations it can be concluded that physical properties of Fe-X-Si-B amorphous alloys, obtained by melt spinning method, depend on the type of alloying element X. A further modification of magnetic and electric properties of these alloys may be achieved by proper heat treatment. The paper presents the results of investigations of the effect of annealing in the temperature range 300-875 K on structure and electric properties occuring in Fe78Si8B14, Fe76Mo2Si8B14 and Fe76Cr2Si8B14 alloys. It was found, based on structural and resistometric investigations, that the addition of Mo and Cr atoms to Fe78Si8B14 alloy caused slower growth of alpha-Fe(Si) crystalline phase in the amorphous matrix. The way of nucleation and the morphology of originating crystalline phases have been analysed and the phase identification has been carried out. A large effect of molybdenum on grains refinement of the precipitated phase has also been observed.