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Advanced Composite Structural Steels for Applications in Heavy Liquid Metals
Husák, Roman ; Haušild, Petr (referee) ; Vilémová,, Monika (referee) ; Hadraba, Hynek (advisor)
Doctoral thesis was focused on preparing of new advanced ODS steels for use in heavy metal liquids enviroments. Possibility of new course for creating oxide dispersion in microstructure was verified by the course of internal oxidation of elements. By the internal oxidation method were prepared new ODS steels strengthened by complex oxides which were created by elements of IIIB and IVB group of elements. Based on analysis of damage ODS steels in LBE were designed surface protection of ODS steel by the oxide layer. The ODS steel protected by oxide layer was subjected to a corrosion test in LBE. For the experiments were chosen class of chromium steels: ferritic-martensitic steel 9Cr1WMnVTa and ferritic steels 14CrWTi and 17Cr1Mo. Steels without oxide dispersion and steel strenghtened by the dispersion based on Y-Ti-O oxides were prepared. On the steels were made series of mechanic tests which should reveal the effectivity of oxide dispersion on the strenght of steel prepared by the internal oxidation method and by the direct addition of oxide elements. It was found that significantly harder oxide material couldn't be fully disrupted through the mechanical alloying and fine oxide dispersion couldn't be created. There was verified fine oxide dispersion could be created by the internal oxidation method and by the direct adding of oxide elements. Same kind of steels strenghtened by new kind of complex oxides based on Y, Ce, Hf, La, Sc and Zr were prepared. The chemical analyses have proven that all added elements could created complex oxide by the reaction with yttrium. The computational analyses for observing of matrix influence and oxide phase influence on strenghtening of steels were performed. These computational analyses were based on microstructural analyses of ODS steels. There was found that the oxide particles could very effectively improve strenght of steels at room temperature and especialy at high temperature. Based on corrosion tests of 14Cr ODS steel in liquid Pb and LBE enviroment were designed surface protection of ODS steel. The effectiveness of protective layer was verified by the high temperature corrosion test of PM2000 in LBE. No damage of oxide layer was observed although Pb and Bi diffused through protective layer.
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Advanced Composite Structural Steels for Applications in Heavy Liquid Metals
Husák, Roman ; Haušild, Petr (referee) ; Vilémová,, Monika (referee) ; Hadraba, Hynek (advisor)
Doctoral thesis was focused on preparing of new advanced ODS steels for use in heavy metal liquids enviroments. Possibility of new course for creating oxide dispersion in microstructure was verified by the course of internal oxidation of elements. By the internal oxidation method were prepared new ODS steels strengthened by complex oxides which were created by elements of IIIB and IVB group of elements. Based on analysis of damage ODS steels in LBE were designed surface protection of ODS steel by the oxide layer. The ODS steel protected by oxide layer was subjected to a corrosion test in LBE. For the experiments were chosen class of chromium steels: ferritic-martensitic steel 9Cr1WMnVTa and ferritic steels 14CrWTi and 17Cr1Mo. Steels without oxide dispersion and steel strenghtened by the dispersion based on Y-Ti-O oxides were prepared. On the steels were made series of mechanic tests which should reveal the effectivity of oxide dispersion on the strenght of steel prepared by the internal oxidation method and by the direct addition of oxide elements. It was found that significantly harder oxide material couldn't be fully disrupted through the mechanical alloying and fine oxide dispersion couldn't be created. There was verified fine oxide dispersion could be created by the internal oxidation method and by the direct adding of oxide elements. Same kind of steels strenghtened by new kind of complex oxides based on Y, Ce, Hf, La, Sc and Zr were prepared. The chemical analyses have proven that all added elements could created complex oxide by the reaction with yttrium. The computational analyses for observing of matrix influence and oxide phase influence on strenghtening of steels were performed. These computational analyses were based on microstructural analyses of ODS steels. There was found that the oxide particles could very effectively improve strenght of steels at room temperature and especialy at high temperature. Based on corrosion tests of 14Cr ODS steel in liquid Pb and LBE enviroment were designed surface protection of ODS steel. The effectiveness of protective layer was verified by the high temperature corrosion test of PM2000 in LBE. No damage of oxide layer was observed although Pb and Bi diffused through protective layer.
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Stress state analysis of sub-sized pre-cracked three-point-bend specimen
Stratil, Luděk ; Kozák, Vladislav ; Hadraba, Hynek ; Dlouhý, Ivo
The contribution deals with finite element analysis of stress state in sub-sized pre-cracked three-point bend specimen (KLST). A studied material was Eurofer´97 steel. The true stress-true strain curve was obtained from tensile test. The three point bend tests were carried out on plain and side-grooved specimens at ambient temperature and were simulated using ABAQUS 6.10. The stress state in KLST specimen was compared with the stress state of standard specimen. The analysis confirmed the stress state in KLST specimens at the crack tip does not correspond to conditions of standard fracture toughness determination because loss of constraint.
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Determination of R-curves from sub-sized three-point-bend geometry
Stratil, Luděk ; Hadraba, Hynek ; Dlouhý, Ivo
Submitted article deals with determination of R-curves from sub-sized three-point-bend geometry. R-curves were measured by single and multi-specimen method on KLST samples fabricated from 25 mm sheet of Eurofer´97 steel. The applicability of single specimen method for given tested geometry and steel was verified. The curves determined by this are well comparable. However results obtained by single specimen method just from one specimen could be biased by material variability. Measured values are in good agreement with published results. The side-grooved specimens show lower values of J-integral and weaker crack-length effect.
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Mechanisms of the embrittelement and the effect of ageing on the brittle-fracture properties of the Eurofer ´97 steel
Stratil, Luděk ; Hadraba, Hynek ; Dlouhý, Ivo
The embrittlement of metal alloys is known phenomenon described as a loss of toughness. This effect is usually caused by segregation of the undesirable traps elements on the grain boundaries or unsuitable precipitation. The iron-based alloys, especially alloyed by chromium, are very susceptible to the embrittlement. The most common mechanisms of the embrittlement of these steels are briefly described in this contribution. The Eurofer´97 is a advanced steel developed for application in nuclear industry mainly alloyed by chromium and tungsten. The susceptibility to the embrittlement of the steel was studied by long-term isothermal ageing. Detailed microstructure studies were carried out in as received and aged state, the fracture behaviour was assessed by instrumented impact tester. The applied ageing caused slight microstructure changes including carbide and subgrain coarsening and slight shift of the impact transition curve.
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The properties of Eurofer´97 steel for developed fusion and fission reactors
Stratil, Luděk ; Hadraba, Hynek ; Dlouhý, Ivo
Ferritic martensitic steel show limited swelling and susceptibility to helium effects and can be made from low activation composition. These properties made them the reference steel for the development of breeding blankets in fusion power plants and also for components of fission power plants. Eurofer´97 is presently being characterized in the EU in order to obtain design data for blanket modules to be tested in International Thermonuclear Experimental Reactor (ITER). In this contribution metallurgical (microstructural and mechanical) properties and thermal thermal treatment for such applications are briefly introduced.
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