Papers by Author: Danuta Stróż

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Authors: Włodzimierz Bogdanowicz, Arkadiusz Onyszko, Jan Rak, Robert Albrecht, Grzegorz Dercz, Aneta Hanc, Andrzej Nowotnik, Danuta Stróż, Józef Lelątko
Abstract: Nickel-based single-crystal superalloys are widely used for production of high pressure turbine blades. The studied blades were obtained in an ALD Vacuum Technologies furnace by the Bridgman technique. Crystallization process was carried out with drawing rates of 3 mm/min and 5 mm/min. The dendrite microstructure based on the γ/γ’ phases and their defects was characterized using X-Ray topography, Laue diffraction, transmission electron microscopy. The defect structure samples were examined with the positron annihilation lifetime spectroscopy. It was found that crystal orientation, lattice parameter of γ’ phase and concentration of defects are correlated. The defect concentration increases in some areas which was the result of deviation of the primary dendrite arm from crystallization direction . Only one type of point defects was detected.
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Authors: Maciej Zubko, Joanna Wspaniała, Danuta Stróż, Enrico Mugnaioli
Abstract: Crystal structure of two spinel single crystals CdCr2Se4 and ZnCr2-xVxSe4 have been reinvestigated using automated electron diffraction tomography method with beam precession. 3D reciprocal space have been reconstructed base on recorded tilt series. For both samples crystal structure was refined and the cubic symmetry with space group Fd-3m was confirmed. No additional electron potential has been located beside occupied atom sites.
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Authors: Henryk Morawiec, Józef Lelątko, Tomasz Goryczka, Krystian Prusik, S. Piechota, Danuta Stróż
Abstract: The Ni-Mn-Ga alloys extruded at high temperature with a relatively large reduction rate were the subject of the studies. The microscopic observations of the transient zone in the extruded rods revealed rotation of the columnar grains in the ingot along the rod axis - giving the preferred <001> orientations. Comparison of the texture, magnetization and magneto-crystalline anisotropy constant for samples cut out from the columnar grain zone and these cut from the extruded rods was carried out for two alloys which differ in chemical composition and Ms temperature. Both alloys have the 5M martensitic structure at room temperature. The samples cut out of the ingot and the extruded rods have shown the axial <001> orientation, similar magnetization curves and magnetocrystalline anisotropy constant Ku = 1.5-1.6 J/m3•105.
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Authors: Krystian Prusik, Katarzyna Reclik, Danuta Stróż, Tomasz Goryczka, Józef Lelątko, Wojciech Gurdziel
Abstract: Two Ni-based (Ni-Mn-Ga and Ni-Mn-Co-In) ferromagnetic nonstoichiometric shape memory alloys were studied in order to determine the influence of hot extrusion process on macro, microstructure and texture of the studied alloys. The microstructure of the alloys in the as cast state and after extrusion was analyzed by electron backscatter diffraction technique. Typical microstructure of the as cast alloys consisted of radially oriented columnar grains elongated perpendicularly to the casting axis. For the alloys Ni-Mn-Ga and Ni-Mn-Co-In alloys the 10M and 14M modulated martensite were observed, respectively. After extrusion Ni-Mn-Ga samples revealed high density of fibre texture parallel to the extrusion axis. In spite of applying different extrusion parameters it was not possible to avoid cracks and overcome the brittleness of the Ni-Mn-Co-In alloys.
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Authors: Eleftheria Maria Pechlivani, Fani Stergioudi, Christos Vogiatzis, Stefanos Skolianos, Danuta Stróż
Abstract: The aim of this paper is to obtain an experimental characterization of glucose-carburized substrates of α-Fe. The carburization process was achieved under vacuum condition using glucose as a carburizing medium. The process was carried out at several temperatures keeping the duration constant at 2h. The samples were treated at 400°C, 650°C and 900°C. The microstructure of the as produced coatings was observed by Scanning Electron Microscopy (SEM) and the formed phases were analyzed by X-Ray Diffraction (XRD). To investigate the corrosion properties of the carburized iron specimens, electrochemical tests were conducted. The samples were exposed to a solution of 3.5% wt. NaCl electrolyte, under quiescent conditions at room temperature and open to the air. The corroded samples were observed with use of Optical Microscopy in order to evaluate the corrosion effect on their surfaces. Carburization of iron samples at temperatures up to 650°C resulted in a shift of the polarization curves to lower current densities. Smaller corrosion rates were measured indicating higher corrosion resistance for these specimens.
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Authors: Krystian Prusik, Katarzyna Bałdys, Danuta Stróż, Tomasz Goryczka, Józef Lelątko
Abstract: In present paper two ribbons of the Ni44Co6Mn36In14 (at.%) were prepared under different melt-spinning technique conditions. Microstructure of the ribbons was studied by scanning electron microscopy (SEM). Depending on the liquid ejection overpressure two types of ribbons microstructures were observed. Ribbon T1 for which ejection overpressure was 1.5 bar showed typical melt-spun ribbon microstructure consisting of a top layer of small equi-axial grains and columnar grains below. For T2 ribbon (ejection overpressure 0.2 bar) only a small fraction of the columnar grains were observed. Structure analysis of the ribbons performed by XRD showed that at room temperature both ribbons have B2 parent phase superstructure. No gamma phase precipitates were observed. In order to determine the orientation of the grains the EBSD technique was applied.
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Authors: Danuta Stróż, Jakub Palka, Zdzisław Lekston
Abstract: In this paper a specific method of severe plastic deformation (SPD) applied to the NiTi shape memory alloy and the obtained structure and the alloy properties are presented. Cold rolling combined with transverse movement of the rolls was the method. The maximal strain obtained was εc ≈ 10.20 for the relatively large specimens. Then the alloy was annealed in order to obtain samples of a given grain size. In the paper the structure of the alloy annealed at 350°C was studied with the use of TEM equipped with Nanomegas attachment ASTAR allowing determination of the orientation of grains in nanoareas.
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Authors: Danuta Stróż, Grzegorz Dercz, Zdzisław Lekston, Jan Rak, Jakub Palka, Jacek Pawlicki
Abstract: Thermomechanical treatment was applied to a binary NiTi alloy in order to improve its functional properties by forming nanocrystalline structure of the alloy. The alloy deformation was obtained by cold rolling combined with transverse movement of the rolls. This technique allowed us to obtain high strain (c ≈ 6) for the relatively large specimens. Subsequently, the samples were annealed in the temperature range 300 -500oC in order to form a nano-, submicro –and/or microcrystalline structure. The evolution of the structure and associated changes of the transformation sequences and functional properties were studied with the use of TEM, X-ray phase analysis, DSC and bend and free recovery ASTM tests. A mixed amorphous/crystalline structure was obtained after severe deformation, the martensitic transformation was completely suppressed in the sample. Annealing at lower temperatures caused formation of nanocrystalline structure that grew to the microcrystalline and finally well-defined polygonized structure in annealed at 500oC specimens.
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Authors: Katarzyna Reclik, Krystian Prusik, Tomasz Goryczka, Marian Kubisztal, Danuta Stróż
Abstract: In the present study the series of the Ni46.2Co5.0Mn36.1In12.6, Ni48.7Co5.2Mn34.4In11.6 and Ni45.6Co4.8Mn36.4In13.2 alloys (at. %) were studied. The influence of the indium addition on structure and phase transitions was studied. All alloys were annealed at 900°C for 24 hours and then slowly cooled in the furnace. After annealing all of the studied alloys showed the macrostructure of radially oriented columnar grains, which lied in the direction perpendicular to the casting axis. For the alloy containing about 13 at. % of indium the monoclinic 14M modulated martensite was stated at room temperature. Apart from the modulated martensite in a1_133 alloy the gamma phase was also observed. For alloy with higher indium content the mixture of cubic L21 parent phase and cubic gamma phase was identified. All studied alloys showed one-step martensitic transformation.
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Authors: Zdzisław Lekston, Danuta Stróż, Magdalena Jędrusik-Pawłowska
Abstract: The effect of plastic deformation by drawing and rolling in the martensite state and final annealing on the structure, grain size, martensitic transformations and shape memory properties of TiNiCo wires is described in the paper. The wires were cold worked by 30 and 40% and then annealed at the temperature range 300-600oC. The structure, phase composition and transformation behaviour of samples after processing and annealing were studied using transmission electron microscopy (TEM), X-ray diffraction (XRD) method and differential scanning calorimetry (DSC) technique. The marformed and annealed at 400 and 450oC wires exhibited a very good superelastic behaviour. The obtained wires were used for production of the shape memory staples with the recovery temperatures close to the human body temperature and as well as for small superelastic staples for fixation of mandible bone fractures.
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