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The fracture behaviour of metallic alloys with low toughness level
Novotný, David ; Svoboda, Jiří (referee) ; Stratil, Luděk (advisor)
The diploma thesis is focused on determining mechanical properties of alloys produced by powder metallurgy methods. Two alloys were studied, namely a highly entropic CrMnFeCoNi alloy and an oxide dispersion-strenthened FeAlO alloy. Both alloys were made in laboratory amount of test material and miniature test specimens were used to measure their mechanical properties. The main goal of the diploma thesis was to develop a crack preparation methodology, to examine and to evaluate the properties of miniature test specimens for materials with low levels of resilience. In the analytical part of the thesis, tensile and deformation properties and fracture toughness of both alloys were measured. For the highly-entropic CrMnFeCoNi alloy, the thesis focused on the effect of the strain rate on the properties of the alloy. For the oxide dispersion-strenthened FeAlO, the effect of temperature in the 23-600 °C temperature range on its mechanical properties was studied.
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The fracture behaviour of metallic alloys with low toughness level
Novotný, David ; Svoboda, Jiří (referee) ; Stratil, Luděk (advisor)
The diploma thesis is focused on determining mechanical properties of alloys produced by powder metallurgy methods. Two alloys were studied, namely a highly entropic CrMnFeCoNi alloy and an oxide dispersion-strenthened FeAlO alloy. Both alloys were made in laboratory amount of test material and miniature test specimens were used to measure their mechanical properties. The main goal of the diploma thesis was to develop a crack preparation methodology, to examine and to evaluate the properties of miniature test specimens for materials with low levels of resilience. In the analytical part of the thesis, tensile and deformation properties and fracture toughness of both alloys were measured. For the highly-entropic CrMnFeCoNi alloy, the thesis focused on the effect of the strain rate on the properties of the alloy. For the oxide dispersion-strenthened FeAlO, the effect of temperature in the 23-600 °C temperature range on its mechanical properties was studied.
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Embrittlement of ferritic 14%Cr ODS steel in air and in Pb/Pb-Bi coolants at elevated temperatures
Hadraba, Hynek ; Dlouhý, Ivo ; Hojná, A. ; Di Gabriele, F.
The work was focused to describing influence of long-time high-temperature exposition of the ferritic 14%Cr ODS steel to the liquid Pb and Pb-Bi metals environments. The steel was during exposition in the liquid Pb and Pb-Bi at 600°C and 550°C respectively depleted from Cr and Ti formed with Pb and Bi the surface oxide scale. In addition the isothermal ageing of the steel at 650°C caused precipitates coarsening and porosity development by dislocation annealing in the bulk of the steel. Tensile and impact bend tests reveals outstanding embrittlement of the isothermally aged ODS steel and the steel after exposition to the liquid Pb and Pb-Bi compared with the steel in as-received state.
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