No (1013)
Yes (4)
Number of found documents:
1017
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IN-SITU HIGH TEMPERATURE LOW CYCLE FATIGUE STUDY OF SURFACE TOPOGRAPHY EVOLUTION IN NICKEL SUPERALLOY
Petrenec, M.; Polák, Jaroslav; Šamořil, T.; Dluhoš, J.; Obrtlík, Karel
2014 - English
In-situ Low Cycle Fatigue test (LCF) at temperature 635 degrees C have been performed in Scanning Electron Microscope (SEM) equipped with Electron Backscatter Diffraction analysis (EBSD) on a small dog-bone-shaped specimen of cast Inconel 713LC superalloy. The aim of the work was to study early stage fatigue damage at high temperature by the observations of the characteristic surface relief evolution and crystallographic characterization changes by EBSD. The detail of slip bands shape was checked by FIB and AFM microscopes. The LCF test was conducted on GATAN stage with pre tilted position and constant stress amplitude of total cycle number of 20. The relief produced in the first cycle determines the other locations of the localized cyclic slip to the primary slip planes (111). The relief was modified in the next cycles but without forming additionally new slip traces in the primary system. Based on EBSD analysis before and after LCF, the orientation of two grains was changed which caused activation of second slip system. The damage mechanism evolution is closely connected with the cyclic strain localization to the persistent slip bands where the fatigue cracks were initiated.
Keywords:
In-situ; SEM; high temperature; fatigue; superalloy
Available at various institutes of the ASCR
IN-SITU HIGH TEMPERATURE LOW CYCLE FATIGUE STUDY OF SURFACE TOPOGRAPHY EVOLUTION IN NICKEL SUPERALLOY
In-situ Low Cycle Fatigue test (LCF) at temperature 635 degrees C have been performed in Scanning Electron Microscope (SEM) equipped with Electron Backscatter Diffraction analysis (EBSD) on a small ...
Analysis of slag material in the production of zinc oxide
Luptáková, Natália; Pešlová, F.
2014 - English
The given paper is closely connected with determination of character and morphology of slag generated in the production of ZnO. Hazardous situations relating to occurrence of these elements are hidden in their ability to create ternary eutectic formations and in terms of mechanical properties, they have ability to create quite fragile structure. The presence of oxygen as well as high temperature causes adhesion of ternary eutectic. Zinc slag has the influence on rapid degradation of the linings and moreover it also decreases the production quality of ZnO. Analysis results are significant information for minimizing of waste material and easier removing of stuck slag.
Keywords:
zinc slag; production of zinc oxide; analysis of slag; phases
Available at various institutes of the ASCR
Analysis of slag material in the production of zinc oxide
The given paper is closely connected with determination of character and morphology of slag generated in the production of ZnO. Hazardous situations relating to occurrence of these elements are hidden ...
On an estimation of the exponent of the stress singularity: three dimensional problems and effect of residual stresses on a crack arrested on the interface
Máša, Bohuslav; Náhlík, Luboš; Hutař, Pavel
2014 - English
The main aim of this paper is an investigation of the crack behavior in the ceramics laminates. Especially, the problem of the estimation of the stress singularity exponent in such a material using different approaches is closely described. Since analytical approach is a suitable tool for two dimensional problems, introducing residual stresses, which can be result of used procedures during composite production, may influence value of the stress singularity exponent. Unfortunately, there is formally no analytical tool available to introduce residual stresses. Moreover, when the three dimensional geometry is investigated, effects of complicated stress distribution in front of the crack tip are of crucial importance for crack behavior. Hence using numerically obtained stress distribution appears to be the only way, how to capture the effect of residual stresses and three dimensional geometry of the crack front. The stress singularity exponent can be directly determined from stress components in front of the crack tip and/or from displacements at faces of the crack. Both can provide good results and give us a solution, which cannot be obtained analytically. In following text the procedure will be described in more detail and shown results obtained on ceramic laminate.
Keywords:
Stress singularity exponent; Residual stress; Singular stress concentrator; Material interface; Ceramic composites
Available at various institutes of the ASCR
On an estimation of the exponent of the stress singularity: three dimensional problems and effect of residual stresses on a crack arrested on the interface
The main aim of this paper is an investigation of the crack behavior in the ceramics laminates. Especially, the problem of the estimation of the stress singularity exponent in such a material using ...
Investigation of Mechanical Properties of Fe3Al-Based Alloys with Vanadium and Carbon Additions by Small Punch Test
Dobeš, Ferdinand; Dymáček, Petr; Kratochvíl, P.; Král, R.; Çelikyürek, I.; Torun, O.
2014 - English
Additions of carbon and carbide-forming elements can positively influence high temperature mechanical properties of alloys based on Fe3Al intermetallic compound. In the present study, the effect of vanadium and carbon additions on mechanical properties of Fe3Al-type alloy is investigated by a combination of small punch tests and conventional tensile and compressive tests. The constant-deflection mode of the small punch test is used to estimate the properties and their temperature dependence. The yield force and the maximum force are evaluated from the force vs. deflection dependence and compared with the corresponding quantities resulting from conventional tests. The comparison is discussed in terms of equations suggested previously by Mao and Takahashi. Modifications suggested recently by Garcia et al. are taken into account as well. Fractographic observations of ruptured specimens are performed with scanning electron microscope. Temperature dependence of small punch test quantities is related to the microscopic image of the fracture. Equivalent fracture strain is evaluated from both small punch test data and microscopic observation of fractured specimens. The relation between equivalent fracture strain and small punch fracture energy is examined. Fracture toughness is calculated from the equivalent fracture strain. Temperature dependence of calculated fracture toughness supports the conclusion that the ductility of investigated alloys is not deteriorated by the presence of carbides.
Keywords:
small punch; yield stress; ultimate tensile strength
Available at various institutes of the ASCR
Investigation of Mechanical Properties of Fe3Al-Based Alloys with Vanadium and Carbon Additions by Small Punch Test
Additions of carbon and carbide-forming elements can positively influence high temperature mechanical properties of alloys based on Fe3Al intermetallic compound. In the present study, the effect of ...
Mechanical alloying of Fe-X (X=Al, Mo, Ni) powders studied by analytical electron microscopy
Buršík, Jiří; Jirásková, Yvonna
2014 - English
Mechanical alloying via ball milling represents a relatively simple way of preparing materials with a micro-to nanograin crystalline and/or amorphous metastable structure.
Keywords:
Fe-X (X=Al, Mo, Ni); SEM and TEM; EDX
Available at various institutes of the ASCR
Mechanical alloying of Fe-X (X=Al, Mo, Ni) powders studied by analytical electron microscopy
Mechanical alloying via ball milling represents a relatively simple way of preparing materials with a micro-to nanograin crystalline and/or amorphous metastable structure.
CARBON DIFFUSION IN CARBON-SUPERSATURATED 9CR-1MO STEEL: ANOMALOUS TEMPERATURE DEPENDENCE OF CARBON DIFFUSIVITY
Čermák, Jiří; Král, Lubomír
2014 - English
Carbon diffusion was studied in temperature interval 573 - 1073 K in carbon-supersaturated surface layer of 9Cr–1Mo steel P91 and in model Fe-15Cr binary alloy. Extremely low carbon diffusion coefficient D (by 3 orders of magnitude lower than the value D eq in material with equilibrium carbon concentration) was observed in carburized surface region of Fe-15Cr. Similar results were obtained for P91 above the temperature T n ~ 800 K. However, below T n , the values of D measured in P91 increased and approached the value of D eq . It seems that the non-Arrhenius behaviour of P91 steel around T n may be ascribed to the α → α + α’ phase decomposition. Possible effect of nitrogen upon the low-temperature increase in D in P91 steel was excluded.
Keywords:
Diffusion; Carbon; phase decomposition; Carbon-supersaturation; Cr-Mo steels
Available at various institutes of the ASCR
CARBON DIFFUSION IN CARBON-SUPERSATURATED 9CR-1MO STEEL: ANOMALOUS TEMPERATURE DEPENDENCE OF CARBON DIFFUSIVITY
Carbon diffusion was studied in temperature interval 573 - 1073 K in carbon-supersaturated surface layer of 9Cr–1Mo steel P91 and in model Fe-15Cr binary alloy. Extremely low carbon diffusion ...
Effect of residual elements on quality of pure zinc
Luptáková, Natália; Pešlová, F.; Stodola, J.
2014 - English
The paper deals with the nature and morphology of the input material for the production of metallic zinc which is used in the production of ZnO through indirect pyrometallurgical processes. The input material is the key parameter in the production of high-quality zinc oxide. For the prediction of complex production process when problematic situation may occur, the systematic analysis of the input zinc raw materials is needed. Undesirable phases in the feedstock can be identified through profound recognition of the source material and the nature of its microstructure. Chemical composition of zinc metal and zinc additives helps to detect the phases occurring in the matrix. Undesirable phases in the feedstock can form (with zinc and other elements) hard and brittle compounds. If these compounds diffuse into the lining during thermal processes, they become the cause of stress in metallurgical ceramics. The emergence of these chemical reactions may subsequently affect the entire metallurgical zinc smelting process. From the microstructure viewpoint, the heterogeneity of grain size, various morphology of intermediate phases, their layout, arrangement, etc. can be expected. The results obtained by analysis are used to minimize waste - zinc slag and to eliminate the conditions which enable the formation of the undesired product, thereby increasing the productivity of the zinc oxide production.
Keywords:
zinc; metallurgical process; phases; residual elements
Available at various institutes of the ASCR
Effect of residual elements on quality of pure zinc
The paper deals with the nature and morphology of the input material for the production of metallic zinc which is used in the production of ZnO through indirect pyrometallurgical processes. The input ...
Crack under biaxial loading: Two-parameter description
Seitl, Stanislav; Bermejo, C. S.
2014 - English
A two-parameter approach for description of stress field for isotropic materials under biaxial loading was proposed in this contribution. From the results, it was found that analysis using the two-parameter fracture mechanics is an effective way to evaluate stress fields under biaxial stress.
Keywords:
Biaxial loading; T-stress; stress intensity factor; crack
Available at various institutes of the ASCR
Crack under biaxial loading: Two-parameter description
A two-parameter approach for description of stress field for isotropic materials under biaxial loading was proposed in this contribution. From the results, it was found that analysis using the ...
MICROSTRUCTURAL INVESTIGATION AND MECHANICAL TESTING OF AN ULTRAFINE-GRAINED AUSTENITIC STAINLESS STEEL
Chlupová, Alice; Man, Jiří; Polák, Jaroslav; Karjalainen, L. P.
2014 - English
Special thermomechanical treatment based on high degree deformation followed by reversion annealing was applied to 301LN austenitic stainless steel to achieve ultrafine-grained (UFG) structure with considerably enhanced mechanical properties. Two different conditions of the thermomechanical treatment were adopted and resulting microstructures with different grain sizes were characterised by optical and high resolution scanning electron microscopy (FEG SEM). Hardness measurements and tensile tests were performed to characterize mechanical properties. To reveal structural changes induced during thermomechanical treatment and during tensile tests a magnetic induction method was additionally applied. Experimental study validated the ability of the treatment to produce an austenitic stainless steel with the grain size of about 1.4 mu m which exhibits tensile strength of around 1000 MPa while ductility remains close to 60 %. The results obtained for both thermomechanical conditions are compared and the relationship between microstructure refinement, phase content and mechanical properties is discussed.
Keywords:
behavior mechanical properties; austenitic steel; ultra-fine grained microstructure; thermomechanical heat treatment; mechanical properties
Available at various institutes of the ASCR
MICROSTRUCTURAL INVESTIGATION AND MECHANICAL TESTING OF AN ULTRAFINE-GRAINED AUSTENITIC STAINLESS STEEL
Special thermomechanical treatment based on high degree deformation followed by reversion annealing was applied to 301LN austenitic stainless steel to achieve ultrafine-grained (UFG) structure with ...
ANALYTICAL ELECTRON MICROSCOPY OF DILUTED CU-CO ALLOYS
Buršík, Jiří; Svoboda, Milan
2014 - English
The work is focused on characterization of diluted model Cu-Co alloys with Co content from 2 to 4 wt.% after various thermal treatment. After initial annealing at 1273 K followed by water cooling, further annealing of the oversaturated solid solution in the range 773 to 1073 K generated a fine distribution of Co-rich precipitates. Parameters of microstructure were characterized by means of transmission electron microscopy with energy dispersive X-ray analysis.
Keywords:
microstructure; behavior; microstructure; analytical electron microscopy; precipitation; Cu alloys
Available at various institutes of the ASCR
ANALYTICAL ELECTRON MICROSCOPY OF DILUTED CU-CO ALLOYS
The work is focused on characterization of diluted model Cu-Co alloys with Co content from 2 to 4 wt.% after various thermal treatment. After initial annealing at 1273 K followed by water cooling, ...
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