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1
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Development of Composites with Icosahedral Phase in Al-Cu-Fe Quasicrystalline Alloys Obtained by the Bridgman Method

100%
Krawczyk J.
Acta Physica Polonica A
|
2014
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vol. 126
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issue 2
501-504
EN
The composites were obtained by the Bridgman method through solidification of Al_{61}Cu_{27}Fe_{12} alloy (numbers indicate at.%). The microstructure of composites with crystal matrix and quasicrystal reinforcement was studied. The crystalline β-phase was the matrix and the quasicrystaline i-phase was the reinforcement of obtained composites. The shape and spatial distribution of reinforcement fibres were specified. Some geometrical relations of the fibres arrangement were defined. Obtained composite samples were subjected to X-ray phase analysis, optical, and scanning electron microscopy observations, chemical microanalysis and the Laue diffraction.
2
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Content available

Dendritic Structure Analysis of CMSX-4 Cored Turbine Blades Roots

100%
Krawczyk J.
Archives of Metallurgy and Materials
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2016
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issue 2
3
Content available remote

A New Approach to Deriving Interatomic Many-Body Interactions in Metals

64%
Gurskii Z., Krawczyk J.
Acta Physica Polonica A
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1998
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vol. 94
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issue 4
671-682
EN
An original method of treating the kinetic and exchange-correlation energies functionals in terms of many particle interactions was developed. It is based on utilizing the local density approximation. The total electron density, extracted from the ab initio band structure calculations, is expressed as a linear superposition of contributions from the individual pseudoions embedded in the uniform background. The explicit expressions for the pair and triplet potentials are presented. The general form for the part of the pair interatomic interactions caused by the kinetic and the exchange-correlation effects is obtained. Relationship between the developing approach and the perturbation theory in pseudopotential is analysed. Unlike the perturbation theory the advanced approach allows one to calculate accurately the so-called reducible contributions to the pair potential arising from the n -particle (n>2) interactions. It corresponds to summing certain series in pseudopotential. Contribution of the electron-nonlocal pseudopotential interactions to the pair interatomic ones is considered within the concept of the fully separable pseudopotentials.
4
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The Influence of Heat Treatment on Microstructure and Tribological Properties of Resistance Butt Welds Made of a Cast Bainitic Steel

64%
Krawczyk J., Parzych S.
Archives of Metallurgy and Materials
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2012
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issue 1
5
Content available remote

Peculiar Thermodynamic Properties of the Falicov-Kimball Model for small U Couplings

64%
Krawczyk J., Lemański R.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
369-371
EN
We analyse a behaviour of the order parameter and specific heat of the Falicov-Kimball model (FKM) on the Bethe lattice using the Dynamical Mean Field Theory (DMFT) formalism, which provides the exact solution in the limit of large spatial dimensions. In the large U limit, the FKM maps onto the effective Ising model, with the order parameter of the Curie-Weiss form. However, in the small U limit the order parameter takes on unusual shape, with a sharp reduction near T ≈ T_{c}/2. We focus our investigation on a crossover between these two limits, thus we perform our calculations for a set of intermediate and small values of U. We find the overall behaviour of the order parameter and specific heat as a function of temperature to be quite anomalous.
6
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Calorimetric and Positron Lifetime Measurements οf Hydrogenated Carbon Nanocones

52%
Budziak A., Dryzek J., Krawczyk J., Zieliński P.
Acta Physica Polonica A
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2010
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vol. 117
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issue 4
574-577
EN
Two carbon nano-structured samples containing 5 and 20% of carbon nanocones in their volume were investigated. Using the Sieverts apparatus the hydrogen was loaded into the samples. The measurements of heat capacity in the temperature range from 100 K to 320 K and the positron lifetime measurements at the room temperature were performed for hydrogenated and non-hydrogenated carbon nanocones. The desorption of hydrogen at the temperature of 230 K is deduced from the heat capacity measurements. The detection of the positronium, the bound state of positron and electron, in the measured samples reveals the presence of open volume defects of ca. 0.198 ± 0.002 nm.
7
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The Mössbauer Spectroscopy Studies οf Cementite Precipitations during Continuous Heating from As-Quenched State of High Carbon Cr-Mn-Mo Steel

52%
Krawczyk J., Bała P., Hanc A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1651-1657
EN
This work complements the knowledge concerning the kinetics of cementite precipitation during tempering. Investigations were performed on 120MnCrMoV8-6-4-2 steel. The samples of investigated steel were austenitized at the temperature of 900°C and quenched in oil. Then four of five samples were tempered. Tempering consisted of heating the samples up to chosen temperatures at the heating rate of 0.05°C/s and fast cooling after reaching desired temperature. This work presents the results of investigations performed carried out using the Mössbauer spectroscopy technique and their interpretation concerning cementite nucleation and growth during tempering. The values of hyperfine magnetic field on ^{57}Fe atomic nuclei, determined for the third component of the Mössbauer spectrum as regards to its intensity, indicate that these are the components coming from ferromagnetic carbides. Big differences in hyperfine magnetic fields coming from Fe atoms existing in the structure of carbides, measured on samples heated up to the temperatures of 80°C and 210°C, in comparison with values for ^{57}Fe atoms precipitated from carbides during heating up to the temperature of 350°C and 470°C, allow to state that these are the carbides of different crystal structure. The influence of hardened steel heating temperature on cementite precipitation was determined. The Mössbauer spectroscopy was applied not only for magnetic hyperfine fileld studies, but also to analyze the values of quadrupole splitting and isomeric shift, which resulted in significant conclusions concerning the changes in cementite precipitations morphology, chemical composition and the level of stresses being present in this research.
8
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The Solid State Polymorphism and Dynamics of 2,3-Dimethylbutan-2-ol (2,3-DM-2-B)

52%
Juszyńska E., Massalska-Arodź M., Zieliński P., Krawczyk J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 4
693-697
EN
In the paper we present adiabatic calorimetry and dielectric spectroscopy results for 2,3-dimethylbutan-2-ol (2,3-DM-2-B), one of the isomers of neohexanol. For 2,3-DM-2-B we have detected the following phase transitions: C2 (249.8 K) → C1 (262 K) → Is. No glass phase was found. In both crystalline phases C2 and C1 three relaxation processes were detected. These processes are discussed in relation to the calorimetric studies.
9
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The Mössbauer Spectroscopy Studies of ϵ to Cementite Carbides Transformation during Isothermal Heating from As-Quenched State οf High Carbon Tool Steel

52%
Bała P., Krawczyk J., Hanc A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1641-1650
EN
This work presents results of investigations using the Mössbauer spectroscopy technique and their interpretation concerning transformation of ϵ to cementite carbides during tempering in relation to the previously conducted dilatometric, microscopic and mechanical investigations. Investigations were performed on 120MnCrMoV8-6-4-2 steel. The influence of the tempering time on nucleation and solubility of ϵ carbides, and on cementite nucleation and growth, was determined. The analysis of phase transformations during various periods of tempering using the Mössbauer spectroscopy technique made possible to reveal fine details connected with the processes.
10
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Premature Cracking of Dies for Aluminium Alloy Die-Casting

52%
Pawłowski B., Tokarski T., Krawczyk J., Bala P.
Archives of Metallurgy and Materials
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2013
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issue 4
11
Content available remote

Mould Walls Inclination and Dendritic Morphology of CMSX-4 Blades Airfoils

52%
Krawczyk J., Bogdanowicz W., Sieniawski J., Kubiak K.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1100-1103
EN
The airfoils of single-crystalline turbine blades were studied. The blades made of industrial CMSX-4 superalloy were obtained by the Bridgman technique. Five different withdrawal rates (1-5 mm/min) were used. Series of as-cast samples were prepared by cutting the airfoils at different distances from the blade root. The metallographic sections, prepared for each cutting planes, were subjected to scanning electron microscopy observations and Laue diffraction studies. Macrostructure images of whole area of airfoil cross-sections were obtained by stitching several obtained SEM images. Morphology of dendrites in different area of cross-sections were analysed. The crystal orientation of each sample were determined by analysis of Laue pattern. It was found that the morphology of dendrites changes in the area, where the dendrite growth is limited by inclined mould walls.
12
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Solid State Polymorphism and Dynamics οf 2,2-Dimethylbutan-1-ol as Studied by Adiabatic Calorimetry and Dielectric Spectroscopy

52%
Juszyńska-Gałązka E., Zieliński P., Massalska-Arodź M., Krawczyk J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
917-925
EN
2,2-dimethylbutan-1-ol, known as neohexanol, was studied by adiabatic calorimetry and dielectric spectroscopy. Details of complex solid state polymorphism and relaxational dynamics were identified and described. System of phases of neohexanol was found to be monotropic with three orientationally disordered crystalline phases besides isotropic liquid and ordered crystal. Moreover, two subsequent glass transition anomalies of heat capacity C_{p}(T) were detected on heating in one of the supercooled orientationally disordered crystalline phases. Thermodynamical properties of neohexanol are described in relation to the dielectric relaxation processes found.
13
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Tribological Properties of Tyre Steel in Rolling-Sliding Contact against Bainitic Rail Steel

52%
Krawczyk J., Witaszek M., Witaszek K.
Archives of Metallurgy and Materials
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2011
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issue 3
14
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Content available

Tribological Properties of Rail Steel in Straight Moderately Loaded Sections of Railway Tracks

52%
Krawczyk J., Bąkowski H., Posmyk A.
Archives of Metallurgy and Materials
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2011
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issue 3
15
Content available remote

On Superconducting Transition Temperature in Amorphous Alloys of Simple Metals

52%
Krasny Y., Kovalenko N., Krawczyk J., Gurnitskaja E.
Acta Physica Polonica A
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1999
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vol. 96
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issue 3-4
457-466
EN
The Eliashberg equations are generalised to describe amorphous binary alloys. Equations for the electron-phonon coupling constant λ are obtained. An additional term caused by topological disorder appears in the expression for λ-constant. The features of amorphous state and their influence on λ-constant and superconducting transition temperature are emphasised and analysed. Theoretical results are illustrated by numerical calculations performed for some binary amorphous alloys of simple metals.
16
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Surface Decorations of Al-Cu-Fe and Al-Cu-Co Single Quasicrystals

52%
Surowiec M., Bogdanowicz W., Krawczyk J., Sozańska M.
Acta Physica Polonica A
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2014
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vol. 126
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issue 2
597-598
EN
We studied surface decorations of faceted icosahedral Al-Cu-Fe and decagonal Al-Cu-Co single quasicrystals by the scanning electron microscopy using primary and secondary electrons. Both types of single quasicrystals exhibited decorations on their facets, however the character of the decorations was totally different. Three kinds of decorations has been developed. On icosahedral Al_{60}Cu_{26}Fe_{14} quasicrystals we found three kinds of decorations: cellular, cavity type and fractal-like. There was no evident difference in chemical composition between the inner dodecahedra and the decorations of all types. Surface decorations found on decagonal Al_{73.5}Cu_{17.5}Co_9 quasicrystals formed a kind of irregular dendritic stars on the separate bright islands.
17
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Fast Stochastic Reorientations in Nematic PAA and PAP

46%
Podsiadły R., Mayer J., Janik J. A., Krawczyk J., Stanek T.
Acta Physica Polonica A
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1997
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vol. 91
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issue 3
513-518
EN
Incoherent quasielastic neutron scattering spectra were measured for nematic para-azoxyanisole (PAA) and para-azoxyphenetole (PAP) with the energy resolution of ca. 30 μ eV, at Dubna IBR-2 reactor. Data processing contained a careful background subtraction and the multiple scattering correction. The corrected spectra were subjected to a reorientational model fitting procedure. For PAA, a model of two convoluted reorientations - that of benzene rings coupled with the terminals and that of the whole molecule around the long molecular axis - gave a fairly good description of the quasielastic neutron scattering spectrum. For PAP, introducing a third motion - interconformational jumps in the ethoxy terminals - in addition to motions suggested for PAA, gave a good agreement with the measured quasielastic neutron scattering spectrum.
18
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Dendrite Growth in Selector-Root Area of Single Crystal CMSX-4 Turbine Blades

46%
Bogdanowicz W., Tondos A., Krawczyk J., Albrecht R., Sieniawski J.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 4
1107-1109
EN
The single crystal turbine blades made of CMSX-4 nickel-based superalloy were studied. The turbine blades were obtained by the Bridgman technique with withdrawal rate of 5 mm/min. The samples, cut-off from root part of blades and containing the fragment of the selector, were studied. The effect of selector geometry on the dendrites growth and defects formation in the selector-root area of the blade were analyzed. The Laue diffraction, scanning electron microscopy, and X-ray diffraction topography were applied. It was found that, during crystallization of the selector, the dendrite cores, after reaching the surface of mould, may bend, if the angle between dendrite cores and the mould surface was equal to 12°. When the angle was equal to 24° the growth of dendrites has been stopped. It can be stated that the defects, which appeared in the selector were inherited by the root part.
19
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Analysis of CMSX-4 Single-Crystalline Turbine Blades Root by Electron and X-Ray Diffraction Methods

46%
Krawczyk J., Zubko M., Bogdanowicz W., Tondos A., Sieniawski J.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 4
1104-1106
EN
The root of single-crystalline turbine blade made of CMSX-4 superalloy were studied. The studied blade was produced by the Bridgman technique in industrial ALD furnace at withdrawal rate of 3 mm/min. The samples for investigations were cut from the blade root parallel to the withdrawal direction. Metallographic sections of longitudinal samples planes were prepared for further investigations. The samples were analysed using scanning electron microscopy and the Laue diffraction studies. The crystal orientations in macro-scale were determined by analysis of the Laue pattern and local crystal orientations were studied by electron backscattered diffraction technique. Morphology of dendrites were examined by analysis of scanning electron microscopy macro-images. Study of subgrain structure was performed by X-ray diffraction topography. The sharp parallel contrast bands, visible on the X-ray topograms, were related with dendrite cores, arranged with the same direction. Additionally, the low angle boundaries were formed in certain samples, visible on the topograms as contrast shifts. Step changes of local crystal orientation in certain areas were observed on the electron backscattered diffraction maps. The electron backscattered diffraction crystal orientation maps were related to the misorientation visualized in topograms.
20
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Molecular Dynamics of 4-Cyano-3-Fluorophenyl 4-Butylbenzoate as Studied by Dielectric Relaxation Spectroscopy

46%
Massalska-Arodź M., Krawczyk J., Juszyńska E., Kocot A., Inaba A.
Acta Physica Polonica A
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2010
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vol. 117
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issue 4
532-536
EN
Dielectric α-relaxation connected with reorientations of the 4-cyano-3-fluorophenyl-4-butylbenzoate molecules around short axes in the isotropic and nematic phases is presented. In the nematic phase the super-Arrhenius temperature dependence of the relaxation has been found. Vitrification of the supercooled nematic phase is shown. Below glass transition temperature the secondary β-relaxation has been identified and described well by the Arrhenius temperature dependence on cooling and on heating. After softening of glass to the metastable nematic phase a spontaneous crystallization occurs as for some other low-weight molecular glass formers.
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