Wyniki wyszukiwania - Biblioteka Nauki

1

Crystallization of amorphous Ni-Zr

100%

Sulejmanovic S. D. , Mihac T. P. , Bikic S. I. , Bajrovic N. A.

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2007

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tom Vol. 28, nr 1-4

160-163

EN

Ni-Zr amorphous alloys (metallic glasses) in the form of ribbon can be prepared in a wide range of concentration which strongly influences their physical properties. Many properties of the metallic glasses differ considerably from those of their crystalline counterparts. In contrast to their crystalline counterparts the resistivities of amorphous alloys are very high. Such high resistivities can be explained by the extra scattering on the random atomic arrangement. Crystallization is the final stage on annealing of metallic glasses. This process is irreversible and is accompanied by abrupt change in electrical resistivity. We have investigated temperature dependance of electrical resistance for different concentrations and for different heating rates. By measuring the electrical resistance the various stages of the crystallization process can be identified.

2

Structure and soft magnetic properties of Fe72B20Si4Nb4 bulk metallic glasses

100%

Nowosielski R. , Babilas R. , Griner S. , Stokłosa Z.

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2009

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tom Vol. 35, nr 1

13-20

EN

Purpose: The paper presents a microstructure characterization, thermal stability and soft magnetic properties analysis of Fe-based bulk amorphous materials. Design/methodology/approach: The studies were performed on Fe₇ ₂B₂ ₀Si₄Nb₄ glassy alloy in form of ribbons and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. The thermal properties of the glassy samples were measured using differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The magnetic properties were determined by the Maxwell-Wien bridge and VSM methods. Findings: The X-ray diffraction and transmission electron microscopy investigations have revealed that the studied as-cast bulk metallic glasses were amorphous. Broad diffraction halo can be seen for all tested samples, indicating the formation of a glassy phase with the diameters up to 2 mm. The fracture surface of rod samples appears to consist of small fracture zones, which leads to breaking of the samples into parts. A two stage crystallization process was observed for studied amorphous alloy. The changes of crystallization temperatures and magnetic properties as a function of glassy samples thickness were stated. Practical implications: The studied Fe-based alloy system has good glass-forming ability and thermal stability for casting bulk metallic glasses, which exhibit good soft magnetic properties, useful for many electric and magnetic applications. Originality/value: The obtained examination results confirm the utility of applied investigation methods in the microstructure, thermal and soft magnetic properties analysis of examined bulk amorphous alloys.

3

Structural changes of Ni-base metallic glasses during thermal activation

100%

Poloczek T. , Griner S. , Nowosielski R.

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2008

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tom Vol. 31, nr 1

33-36

EN

Purpose: The paper presents a crystallization process of i68.7Cr6.6Fe2.65Si7.8B14C0.25 metallic glasses. The Ni68.7Cr6.6Fe2.65Si7.8B14C0.25 metallic glasses was produced by the CBMS method with cooling rate corresponding for amorphous structure manufacturing. Design/methodology/approach: The crystallization of Ni68.7Cr6.6Fe2.65Si7.8B14C0.25 metallic glasses by method internal friction (IF) differential thermal analysis (DTA), X-ray and transmission electron microscopy (TEM) were studied. Findings: The investigation showed, that metallic glasses during thermal activation go through from metastable amorphous state by few medial states to the stable crystalline state (relaxation and crystallization process). Research limitations/implications: During thermal activation of metallic glasses two processes can be distinguished: structural relaxation of amorphous structure and complex crystallization process of alloy. Practical implications: Perception of structural relaxation and crystallization processes of metallic glasses can used for analysis of thermal stability of metallic glasses. Originality/value: The paper presents, that the thermal activation of metallic glasses conduct to the structural changes, which the final stage is crystalline state.

4

Determination of thermal and mechanical properties of Ni63Cu9Fe8P20 amorphous alloy

100%

Ziewiec K. , Kurtyka P.

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2006

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tom Vol. 51, iss. 2

217-220

EN

Nickel-copper-iron-phosphorus Ni63Cu9Fe8P20 alloy was cast using melt spinning method. The ribbons in as cast state are characterized with use of TEM and X-ray diffraction. Then the ribbons were heated in DTA up to different temperatures and then characterized with use of X-ray diffraction to see the change of the microstructure after heating to elevated temperatures. The melt-spun ribbons in as-cast state were preliminarily compacted in a die and then compressed. The mechanical characteristics of the compacted ribbons at different temperatures were registered.

PL

Stop niklu, miedzi, żelaza i fosforu o składzie Ni63Cu9Fe8P20 odlewano metodą „melt spinning”. Otrzymane taśmy w stanie po odlewaniu były badane przy pomocy transmisyjnego mikroskopu elektronowego (TEM) oraz dyfraktometru rentgenowskiego. Następnie taśmy nagrzewano w różnicowym analizatorze termicznym (DTA) do różnych temperatur a następnie były one ponownie badane przy pomocy dyfraktometru rentgenowskiego. Po odlewaniu metodą „melt spinning” taśmy były wstępnie prasowane w matrycy w celu otrzymania pastylek a następnie poddawane próbie ściskania. Rejestrowano charakterystyki mechaniczne prasowanych taśm przy różnych temperaturach.