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The effect of σ-phase formation on long-term durability of SUPER 304H steel
Horváth, J.; Král, Petr; Janovec, J.; Sklenička, Václav
2015 - anglický
This work presents results of the analysis of phases formed in a SUPER 304H steel during a medium-term static isothermal ageing (675 degrees C/15000 h). The investigations of the precipitates were especially focused on the occurrence of sigma-phase because its formation leads to the serious embrittlement. \nThe evaluation and distribution of brittle sigma-phase were determined on macroscopic level by using light microscopy/colour etching. The microstructure was also investigated on microscopic level by scanning electron microscopes Tescan Lyra 3 and JEOL JSM 5410 equipped by electron backscatter diffraction unit and by transmission electron microscope Jeol 2100F. This work also investigates the effect of sigma-phase formation on the impact strength of an aged state of SUPER 304H steel. For comparison reasons the microstructure and the mechanical properties of the initial as-received) state were also investigated. It was found that the formation of brittle sigma-phase in the aged and therefore degraded microstructure led to the significant decrease of the impact strength. The influence of brittle sigma-phase on long-term durability of the degraded steel regarding its insufficient impact strength is discussed.
Klíčová slova:
austenitic steel; medium-term ageing; SUPER 304H; sigma-phase; impact strength
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The effect of σ-phase formation on long-term durability of SUPER 304H steel
This work presents results of the analysis of phases formed in a SUPER 304H steel during a medium-term static isothermal ageing (675 degrees C/15000 h). The investigations of the precipitates were ...
Deposition of Hard Yet Moderately Ductile MoBC Coatings by p-DC Magnetron Sputtering
Souček, P.; Buršíková, V.; Zábranský, L.; Buršík, Jiří; Vašina, P.
2015 - anglický
Novel nanolaminated MoBC coatings were prepared using a combination of non-reactive direct current and pulsed direct current magnetron sputtering. Depending on the deposition conditions the coatings were either of amorphous or of nanocomposite nature. Nanocomposite coatings showed good hardness and Young’s modulus and showed no tendency to form cracks even for high-load nanoindentation testing.
Klíčová slova:
magnetron sputtering; ion flux; nanolaminates
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Deposition of Hard Yet Moderately Ductile MoBC Coatings by p-DC Magnetron Sputtering
Novel nanolaminated MoBC coatings were prepared using a combination of non-reactive direct current and pulsed direct current magnetron sputtering. Depending on the deposition conditions the coatings ...
Chemical Wet Synthesis and Characterization of Copper-Silver Nanoparticles
Zobač, O.; Sopoušek, J.; Vykoukal, V.; Buršík, Jiří; Roupcová, Pavla
2015 - anglický
AgCu nanoparticles (NPs) of near-eutectic composition were prepared by various route of wet synthesis. Nanoparticles suspended in nonpolar solvents were synthesized by solvothermal synthesis from metalloorganic precursors. AgCu colloids in aqueous solution were obtained by the hydride reduction of Ag and Cu nitrates under action of different stabilization agents. Chemical characterizations of as-synthesized AgCu NPs were done using inductively-coupled plasma-optical emission spectrometry (ICP-OES). The optical properties of nanoparticles were monitored using UV-Vis spectrophotometer. The size of colloid nanoparticles were measured by both dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) method in some extra cases.
Klíčová slova:
nanoalloy; Ag-Cu; phase transformation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Chemical Wet Synthesis and Characterization of Copper-Silver Nanoparticles
AgCu nanoparticles (NPs) of near-eutectic composition were prepared by various route of wet synthesis. Nanoparticles suspended in nonpolar solvents were synthesized by solvothermal synthesis from ...
Analysis of the surface layer of the brake disk
Švábenská, Eva; Roupcová, Pavla; Podstranská, Ivana; Petr, M.; Filip, J.; Schneeweiss, Oldřich
2015 - anglický
Our research is focused on the changes in thin surface layer of the brake disk due to the impact of severe plastic deformation and heating by friction process. The aim of this study is to compare structure, chemical and phase compositions of the surface layer in depth up to several hundreds of nanometers in the no affected central part of brake disk and the part which was in contact with brake pads by braking. The basic information on structure and phase composition was obtained by optical and scanning electron microscopy, X-Ray Powder Diffraction and Mössbauer Spectroscopy. The thin surface layer was studied using Conversion Electron Mössbauer Spectroscopy and X-ray Photoelectron Spectroscopy. We explain the observed changes with the knowledge on effects of plastic deformation and/or diffusion of alloying elements in the material of the brake disk.
Klíčová slova:
grey cast iron; brake disk; microstructure analysis; surface layer
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Analysis of the surface layer of the brake disk
Our research is focused on the changes in thin surface layer of the brake disk due to the impact of severe plastic deformation and heating by friction process. The aim of this study is to compare ...
THE EFFECTS OF HIGH TEMPERATURE HELIUM GAS ON THE FRACTURE BEHAVIOUR OF ODS MA957
Rozumová, L.; Hojná, A.; Kalivodová, J.; Bublíková, P.; Hadraba, Hynek; Di Gabriele, F.
2015 - anglický
Oxide-dispersion-strengthened steel (ODS) MA957 has been studied as a candidate material for Tritium Breeding Blanket for fusion reactors with helium coolant, where temperatures 250-650 degrees C are expected. Helium is one of type as primary coolant in High Temperature Reactor and Gas Cooled Fast Reactor with working temperature 500-1000 degrees C. \n\nThis work presents results of the study of behaviour of ODS (MA957) under influence of high temperature helium environment. Microstructure of the material and the interaction with He was investigated. The average exposure temperature was held at 720 degrees C. Subsequently, the surface changes were determined. Impact testing and material surfaces were studied in detail by means of SEM and TEM microscopy. It is essential to understand the He effect on microstructure and mechanical properties of structural materials since the He embrittlement in TBB may be significant.
Klíčová slova:
ODS; MA957; Helium
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
THE EFFECTS OF HIGH TEMPERATURE HELIUM GAS ON THE FRACTURE BEHAVIOUR OF ODS MA957
Oxide-dispersion-strengthened steel (ODS) MA957 has been studied as a candidate material for Tritium Breeding Blanket for fusion reactors with helium coolant, where temperatures 250-650 degrees C are ...
THE INFLUENCE OF CONSOLIDATION PROCEDURE PARAMETERS ON COMPACTION OF AL POWDER
Lowe, T. C.; Kunčická, L.; Kocich, R.; Davis, C. F.; Hlaváč, L.; Dvořák, Jiří
2015 - anglický
The influence of different consolidation procedures on compaction of Al powders was evaluated. Powder preparation procedures consisted of selection of particle size distribution, cold isostatic pressing (CIP), and vacuum sintering. Processing parameters investigated included the number of compression steps, compression pressure, and sintering temperature and time. Densities of the samples after compression and also after sintering were measured and compared. The overall oxygen content was analysed using by Energy Dispersive Spectroscopy. Phase composition was determined using X-ray. Microhardness measurements were performed to evaluate the degree of compaction. Double-step CIP at 200+300 MPa and subsequent sintering at 500°C for 60 min produced the best combination of properties from all the consolidation technologies of Al particles. Of the particle size ranges studies, those with diameters between 20 and 45 μm produced the best results. Aluminum oxide was present in the structure after all the processing treatments.
Klíčová slova:
Aluminum powder; cold isostatic pressing; sintering; oxygen content; X-ray
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
THE INFLUENCE OF CONSOLIDATION PROCEDURE PARAMETERS ON COMPACTION OF AL POWDER
The influence of different consolidation procedures on compaction of Al powders was evaluated. Powder preparation procedures consisted of selection of particle size distribution, cold isostatic ...
ATOMISTIC SIMULATIONS OF TWIN BOUNDARIES FACETING IN HCP MATERIALS
Ostapovets, Andriy
2015 - anglický
Deformation twinning is frequently observed in materials with hexagonal crystal lattice. It plays important role in plastic deformation of such materials. Twin regions have often lamellar shape and twin boundaries are usually oriented along invariant planes. However, non-invariant plane twin interfaces are also observed. Occurrence of such interfaces can be connected with interactions between twinning disconnections. Mechanisms of such interactions are discussed on the basis of atomistic simulations.
Klíčová slova:
Twin boundaries; hcp; EAM potential
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
ATOMISTIC SIMULATIONS OF TWIN BOUNDARIES FACETING IN HCP MATERIALS
Deformation twinning is frequently observed in materials with hexagonal crystal lattice. It plays important role in plastic deformation of such materials. Twin regions have often lamellar shape and ...
Ab initio calculations of temperature dependent resistivity for transition metals
Wagenknecht, D.; Turek, Ilja; Carva, K.
2015 - anglický
The effect of phonons on electrical resistivity has been simulated by considering random displacements of atomic nuclei from their equilibrium positions together with a frozen-potential approach. The developed theory has been applied successfully to late transition metals (Fe, Ni, Rh, Pd, Pt).
Klíčová slova:
electrical resistivity; temperature dependence; transition metals
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Ab initio calculations of temperature dependent resistivity for transition metals
The effect of phonons on electrical resistivity has been simulated by considering random displacements of atomic nuclei from their equilibrium positions together with a frozen-potential approach. The ...
Effect of grit blasting surface treatment on high temperature low cycle fatigue life of Inconel 713LC
Šulák, Ivo; Obrtlík, Karel; Čelko, L.; Gejdoš, P.
2015 - anglický
This paper presents the results of high temperature low cycle fatigue tests carried out on Inconel 713LC. This polycrystalline nickel based superalloys is mainly used for high temperature applications such as disks, blades and vanes of gas turbine engines. These machine components are manufactured by investment casting and undergo a series of postcast processes to remove remnants of shells, oxides and other contaminants. Grit blasting is one of the most widely used and cheapest technology ensuring adequate cleaning of the surface and at the same time is used to treat the substrate surface prior to application of metalic bond coat and various protective coatings (like diffusion, overlay or thermall barier coatings). Low cycle fatigue tests were conducted on as-received and grit blasted material in fully reversed pull-push cycle in strain control mode with constant total strain amplitude and strain rate at 900 °C in air. Experimental data on fatigue life were evaluated and parameters of Baquin and Coffin-Manson curves were obtained for both tested materials. Specimen surface and cross sections of both treated and untreated materials were analysed prior to fatigue tests and also after testing by means of optical microscopy (OM), as well as scaning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and Vickers microhardness was measured. Fatigue degradation mechanisms was documented in both materials and negligible effect of grit blasting on low cycle parameters was discussed.
Klíčová slova:
Grit blasting; Surface relief; Surface microhardnes; High temperature fatigue life; Inocel 713LC
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Effect of grit blasting surface treatment on high temperature low cycle fatigue life of Inconel 713LC
This paper presents the results of high temperature low cycle fatigue tests carried out on Inconel 713LC. This polycrystalline nickel based superalloys is mainly used for high temperature ...
Analysis of nanoparticles released from the car brakes
Švábenská, Eva; Roupcová, Pavla; Schneeweiss, Oldřich
2015 - anglický
Our research is focused on the phase, structure and chemical analysis of the powder particles released by braking of cars from their brake components – discs and pads. The basic information on structure and phase composition was obtained by X-Ray Powder Diffraction, Mössbauer Spectroscopy and scanning electron microscopy with EDX. The results of the particle analysis are compared with materials used for manufacturing brake components and with the powder prepared by ball milling of the mixture of the pad composite and disk steel. Most of recognized nanoparticles are based on carbon, silica/silicates and iron oxides. Their effects on street environment are mentioned.
Klíčová slova:
nanoparticles; wear debris; automotive brake
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Analysis of nanoparticles released from the car brakes
Our research is focused on the phase, structure and chemical analysis of the powder particles released by braking of cars from their brake components – discs and pads. The basic information on ...
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