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    Wyświetlanie 1-9 z 9
    Tytuł:
    Tunneling and Point Contact Spectroscopy of High-T$\text{}_{c}$ Superconducting Thin Films
    Autorzy:
    Seidel, P.
    Grajcar, M.
    Plecenik, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1968767.pdf
    Data publikacji:
    1998-02
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.80.Fp
    73.40.Gk
    74.50.+r
    Opis:
    Tunneling and point contact junctions between a normal metal and thin high temperature superconducting film were studied to obtain information on surface properties. Surface degradation and time development of contact resistance are investigated as well as peculiarities of the conductance-voltage characteristics. The quasi-linear background is related to carrier transport through degraded surface layer described by a model of inelastic scattering from a broad flat continuum of states inside the potential barrier. An asymmetry of the characteristics appears as the result of low Fermi energy values in the high temperature superconductors in comparison to common metals. An extrinsic nature of these peculiarities is supported by effects of barrier formation by applied voltages in the 1 volt range. As an often observed anomaly a conductance peak at zero bias is observed which can be related to different mechanisms. In the case of high temperature superconductors this zero bias anomaly is related to the d-wave pairing symmetry of the pair potential. Experimental results on YBCO and BSCCO films are compared to calculations taking into account the Andreev reflections for a junction between a normal metal and a d-wave superconductor.
    Źródło:
    Acta Physica Polonica A; 1998, 93, 2; 355-363
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Superconductivity Near Transition to Insulating State in MoC Ultrathin Films Studied by Subkelvin STM
    Autorzy:
    Szabó, P.
    Neilinger, P.
    Trgala, M.
    Grajcar, M.
    Samuely, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1372334.pdf
    Data publikacji:
    2014-07
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    74.50.+r
    74.78.-w
    74.81.-g
    Opis:
    We study the homogeneously disordered MoC thin films with thicknesses of 10 and 5 nm and the superconducting transition temperatures near 6 and 4 K, significantly decreased as compared to the bulk $T_{c}$=8.32 K due to a disorder. The scanning tunnelling spectroscopy reveals in the thicker sample a BCS superconducting energy gap Δ with a broadening parameter Γ equal to about 10 per cent of Δ. Remarkably, Γ increases with temperature. The thinner, more disordered sample shows a gapped superconducting density of states but without any coherence peaks at the gap edge, which could not be approximated by the BCS DOS. Moreover, the reduced DOS around the Fermi level persists above the resistive transition temperature reminding the pseudo-gap known from high-$T_{c}$ cuprates.
    Źródło:
    Acta Physica Polonica A; 2014, 126, 1; 368-369
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modification of non-metallic inclusions by rare-earth elements in microalloyed steels
    Autorzy:
    Opiela, M.
    Grajcar, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/382841.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    pierwiastki ziem rzadkich
    wtrącenia niemetaliczne
    stal mikrostopowa
    rare earth elements (REE)
    non-metallic inclusions
    microalloyed steels
    Opis:
    The modification of the chemical composition of non-metallic inclusions by rare-earth elements in the new-developed microalloyed steels was discussed in the paper. The investigated steels are assigned to production of forged elements by thermomechanical treatment. The steels were melted in a vaccum induction furnace and modification of non-metallic inclusions was carried out by the michmetal in the amount of 2.0 g per 1 kg of steel. It was found that using material charge of high purity and a realization of metallurgical process in vacuous conditions result in a low concentration of sulfur (0.004%), phosphorus (from 0.006 to 0.008%) and oxygen (6 ppm). The high metallurgical purity is confirmed by a small fraction of non-metallic inclusions averaging 0.075%. A large majority of non-metallic inclusions are fine, globular oxide-sulfide or sulfide particles with a mean size 17 m2. The chemical composition and morphology of non-metallic inclusions was modified by Ce, La and Nd, what results a small deformability of nonmetallic inclusions during hot-working.
    Źródło:
    Archives of Foundry Engineering; 2012, 12, 2; 129-134
    1897-3310
    2299-2944
    Pojawia się w:
    Archives of Foundry Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study on Non-Metallic Inclusions in Laser-Welded TRIP-Aided Nb-Microalloyed Steel
    Badania wtrąceń niemetalicznych w spawanej laserowo stali TRIP z mikrododatkiem Nb
    Autorzy:
    Grajcar, A.
    Różański, M.
    Kamińska, M.
    Grzegorczyk, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/352327.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    TRIP steel
    non-metallic inclusions
    laser welding
    multiphase microstructure
    retained austenite
    fusion zone
    heat-affected zone
    stal TRIP
    wtrącenia niemetaliczne
    spawanie laserowe
    mikrostruktura
    austenit szczątkowy
    strefa przetopienia
    strefa wpływu ciepła
    Opis:
    The work concerns the studies on non-metallic inclusions occuring in laser-welded Si-Al TRIP steel containing Nb and Ti microadditions. Laser welding tests of 2 mm thick thermomechanically rolled sheets were carried out using keyhole welding and a solid-state laser. The results of laser welding in the air atmosphere for the heat input value of 0.048 kJ/mm are included. The distribution, type and chemical composition of non-metallic inclusions formed in the base metal, heat-affected zone, and fusion zone are analysed in detail. It was found that the base metal contains rare, fine oxysulphides. Their chemical composition was modified by rare earth elements. Numerous oxide inclusions of a various size and a chemical composition occur in the fusion zone. The dependence between a size of particles and their chemical composition was observed. A microstructure of steel was assessed using light microscopy and scanning electron microscopy techniques.
    Praca dotyczy badań wtrąceń niemetalicznych występujących w przetapianej laserowo stali TRIP typu Si-Al zawierającej mikrododatki Nb i Ti. Próby spawania laserowego odwalcowanych termomechanicznie taśm o grubości 2 mm przeprowadzono z wykorzystaniem lasera na ciele stałym i techniki głębokiego przetopienia. Przedstawiono wyniki przetapiania laserowego próbek z energią liniową 0.048 kJ/mm w atmosferze powietrza. Szczegółowej analizie poddano rozkład, rodzaj i skład chemiczny wtrąceń niemetalicznych tworzących się w materiale rodzimym, strefie wpływu ciepła i strefie przetopionej. Stwierdzono, że w materiale rodzimym występują nieliczne, drobne wtrącenia siarczkowo-tlenkowe, których skład chemiczny został zmodyfikowany przez pierwiastki ziem rzadkich. W strefie przetopionej występują liczne wtrącenia tlenkowe o zróżnicowanej wielkości i składzie chemicznym. Zaobserwowano zależność między wielkością wtrąceń a ich składem chemicznym. Mikrostrukturę stali określono z wykorzystaniem mikroskopii świetlnej i skaningowej mikroskopii elektronowej.
    Źródło:
    Archives of Metallurgy and Materials; 2014, 59, 3; 1163-1169
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modified Twin-Spot Laser Welding of Complex Phase Steel
    Autorzy:
    Różański, M.
    Morawiec, M.
    Grajcar, A.
    Stano, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/356531.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    laser welding
    complex phase steel
    metallurgical weldability
    fine-grained microstructure
    twin-spot welding
    Opis:
    The work addresses modified methods of twin-spot laser welding of complex phase steel sheets and investigates the effects of laser beam distribution on the macrostructure, microstructure and hardness. The research-related results were obtained for the beam power distributions of 50%-50%, 60%-40% and 70%-30%. Test joints were made using a Yb:YAG disc laser with a maximum power of 12 kW and a welding head by means of which it was possible to focus a laser beam on two spots. It was found that the change in the laser beam distribution affects geometrical features of the joint. The application of the second beam of lower power enables obtaining tempering-like effects, which finally lead to the beneficial hardness reduction both in the fusion zone and in heat-affected zone. The identification of various microstructural constituents in different zones of the joint was performed using light microscopic micrographs and scanning electron images.
    Źródło:
    Archives of Metallurgy and Materials; 2016, 61, 4; 1999-2008
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Combined effects of strain and cooling path on hot deformation response and microstructure of low-carbon structural steel
    Autorzy:
    Morawiec, M.
    Borek, W.
    Mroziński, M.
    Grajcar, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/379077.pdf
    Data publikacji:
    2019
    Wydawca:
    Stowarzyszenie Komputerowej Nauki o Materiałach i Inżynierii Powierzchni w Gliwicach
    Tematy:
    structural steel
    low-carbon steel
    hot deformation
    thermomechanical process
    gleeble simulator
    cooling path
    stal konstrukcyjna
    stal niskowęglowa
    odkształcenie na gorąco
    proces termomechaniczny
    symulator Gleeble
    droga ochładzania
    Opis:
    Purpose: The aim of the paper is to analyse the effect of thermomechanical process with different cooling paths on microstructure and mechanical properties of low-carbon structural steel. Design/methodology/approach: The steel used for the investigation was subjected to two step deformation using a Gleeble 3800 simulator and then held at designed temperatures from 650ºC to 800ºC for different times. A final step included water cooling to room temperature to freeze the microstructure. Typical microscopic studies have been done. The analysis of the volume fraction of presented phases was carried out together with the measurement of grain size by means of image analysis. The last part of conducted research was hardness analysis of the steel after the different heat treatments. Findings: It was found that the microstructure constitution and grain size are strongly dependent on the temperature of isothermal holdings. The microstructure of steel held at 800ºC is composed of the mixture of bainite and two kinds of ferrite: globular and acicular. When the temperature was lowered by 50ºC the ferrite shows the globular morphology. When the temperature drops to 700ºC and below it, the microstructure is composed of ferritic-pearlitic mixture. It was observed that when the isothermal temperature was increased the grain size decreased and the opposite effect was observed for the holding time. The longer the time of the isothermal holding, the larger was the grain size. Research limitations/implications: For better understanding of the phase transformation kinetics in this steel the dilatometric test are planned. Practical implications: The knowledge of the microstructure evolution and hot deformation response of low-carbon structural steels is important from the industrial point of view. Originality/value: The combined effects of hot deformation and different cooling paths give the useful information on a microstructure evolution.
    Źródło:
    Archives of Materials Science and Engineering; 2019, 95, 1; 5-11
    1897-2764
    Pojawia się w:
    Archives of Materials Science and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Microstructure-Properties Relationship and Mechanical Stability of Retained Austenite in Thermomechanically Processed Medium-C TRIP Steel at Different Deformation Temperatures
    Autorzy:
    Skowronek, A.
    Kozłowska, A.
    Grajcar, A.
    Morawiec, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/354757.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    TRIP effect
    multiphase steel
    retained austenite
    mechanical stability
    deformation temperature
    Opis:
    The paper presents the effect of deformation temperature on the mechanical stability of retained austenite in a multiphase TRIP steel. Series of static tensile tests were carried out in the temperature range –20 to 140°C in order to simulate the temperatures occurring during stamping process of automotive steel sheets and conditions of their exploitation. Samples deformed at 20°C and 60°C showed the best combination of strength and ductility. It was related to the gradual transformation of retained austenite into martensite. Obtained results revealed that the intensity of TRIP effect is significantly related to the deformation temperature. The amount of retained austenite, which transformed into martensite during plastic deformation decreases as the deformation temperature increases. It was also found that the stability of retained austenite depends on its morphology. The obtained results showed the relationship between deformation temperature and the stability of retained austenite. The chemical composition and microstructure of multiphase steels dedicated to the automotive industry should be designed for providing the maximum TRIP effect at the specific deformation temperatures.
    Źródło:
    Archives of Metallurgy and Materials; 2020, 65, 2; 941-949
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Microstructural Aspects of Bifocal Laser Welding of TRIP Steels
    Autorzy:
    Grajcar, A.
    Grzegorczyk, B.
    Różański, M.
    Stano, S.
    Morawiec, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/355074.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    TRIP steel
    retained austenite
    dual beam
    laser welding
    AHSS
    hardness profile
    Opis:
    This work is concerned with comparative tests involving single-spot and twin-spot laser welding of thermomechanically rolled TRIP steel. The welding tests were carried out using keyhole welding and a solid state laser. In the case of twin-spot laser beam welding, the power distribution of beams was 50%:50%. The changes in macro- and microstructures were investigated using light and scanning electron microscopy. Three main zones subjected to the tests included the fusion zone, the heat affected zone and the intercritical heat affected zone (transition zone between the base material and the HAZ). Special attention was paid to the effect of various thermal cycles on the microstructure of each zone and on martensite morphology. The tests involved hardness measurements carried out in order to investigate the effect of different microstructures on mechanical properties of welds.
    Źródło:
    Archives of Metallurgy and Materials; 2017, 62, 2A; 611-618
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Microstructural Aspects of Twin-Spot Laser Welding of Dp-Hsla Steel Sheet Joints
    Autorzy:
    Stano, S.
    Grajcar, A.
    Wilk, Z.
    Różański, M.
    Matter, P.
    Morawiec, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/352264.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    DP steel
    HSLA steel
    weldability
    overlap joint
    twin-spot welding
    Opis:
    The article presents the possibility of using twin-spot laser welding (i.e. laser welding with focusing a laser beam on two spots) for making overlap joints made of 0.8-1 mm thick HSLA and DP type high strength steel sheets. Joints were made using a Yb:YAG disc laser having a maximum power of 12 kW and a welding head by means of which it was possible to focus a laser beam on two spots, 0.6 mm and 1 mm away. The angle between focuses amounted to 0° or 90°, whereas the power distribution was 50%-50%. With settings as presented above it was possible to obtain high-quality overlap joints. The geometrical parameters of the joints were primarily affected by beams positions (in relation to each other) and, to a lesser degree, by the distance between the focuses. It was possible to obtain a 10% hardness reduction in the fusion zone of the DPHSLA steel joints if the angle between the beams amounted to 90°. The tests also involved microstructural examinations of individual zones of the joints.
    Źródło:
    Archives of Metallurgy and Materials; 2016, 61, 2A; 731-740
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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