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High-temperature embrittlement of 14%Cr ODS ferritic steel in liquid lead environment
Dohnalová, Eva ; Čelko, Ladislav (referee) ; Hadraba, Hynek (advisor)
The thesis deals with the high-temperature embrittlement of 14%Cr ODS ferritic steel in liquid lead environment. The 14%Cr ferritic ODS steel ODM401 manufactured by powder metallurgy technology was used as an experimental material. The effect of the long-term annealing, surface corrosion attack in the melt Pb and Pb-Bi on the microstructure and mechanical properties was described. The subsequent microstructural changes were evaluated by means of scanning electron microscopy and transmission electron microscopy The mechanical behaviour of the experimental material was proven by means of microhardness test, impact test and static tensile test. The fractographical evaluation of fracture surfaces were performed on all samples. The surface attack and outstanding microstructural ganges were found after the long-time exposition of the steel in Pb/Pb-Bi melts at temperature 550°C/1000h and 500°C/1000h respectively. The embrittlement of the steel after exposition in Pb/Pb-Bi melts was comparable to the embrittlement after high-temperature annealing of the steel at temperature 650°C/1000h.
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New compositions of advanced oxide dispersion steels based on rare earth elements
Pech, Filip ; Kuběna, Ivo (referee) ; Hadraba, Hynek (advisor)
The main objective of present diploma thesis is to prepare three different classes of steels, differing by their content of chromium: 9Cr, 14Cr, 17Cr steels and their oxide dispersion strengthened variants. Steels were prepared from atomic and pre-alloyed powders by the mechanical alloying and compacted by the spark plasma sintering method. Used strengthening elements were yttrium, which is most commonly used, and aluminium. Preparation of oxide dispersion was done in two ways: direct adding of yttria and alumina and inner oxidation of aluminium and yttrium. In the experimental part has been found, that it is possible to make oxide dispersion by both ways, but aluminium strengthened steel has to be prepared by inner oxidation to ensure fine oxide dispersion.
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Characterization of oxide dispersion strengthened alloys prepared from various precursor materials
Dobrovolný, Tomáš ; Havlík, Petr (referee) ; Moravčík, Igor (advisor)
Submitted master’s thesis studies the influence of input precursors (powders) on the resulting properties of prepared steels. When manufactured using the mechanical alloying method, the input powders can have a significant effect on the resulting properties. The austenitic steel 15-15Ti (1.4970) was chosen as the prepared alloy, which is gradually beginning to find application in nuclear energy. In this work, two approaches were used to produce this steel powder, firstly the production of an alloy from the precursor powder of austenitic steel AISI 304L and secondly the alloy was produced only from pure elements. For each of these methods, two different milling conditions were chosen. Thus, a total of four mixtures of 15-15Ti austenitic steel powders were produced, which were sintered into bulk materials using the SPS method. Mechanical properties of sintered specimens were tested by a tensile test and a hardness measurement by Vickers hardness test. At the same time, microstructure analysis using SEM and phase composition analysis by XRD were performed, both for prepared powders and for sintered bulks.
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Early Stages of Fatigue Damage of Steels for Fusion Energetics
Kuběna, Ivo ; Spätig, Philippe (referee) ; Lukáš, Petr (referee) ; Kruml, Tomáš (advisor)
Hlavním cílem této práce bylo vysvětlit únavové chování ocelí ODS Eurofer, 14Cr ODS feritické oceli vyráběné v CEA (Commissariat a l’énergie atomique, Saclay, France) a 14Cr ODS feritické oceli vyráběné v EPFL (École Polytechnique Fédérale de Laussane, Switzerland). Pokud to bylo možné byly získané výsledky porovnány s ocelí Eurofer 97. Tato práce je součástí široké spolupráce, která je zaměřena na vývoj konstrukčních materiálů pro fuzní reaktory. V průběhu práce byly provedeny následující experimenty: • Standardní únavové zkoušky za pokojové teploty, při 650 a při 750 , byly získány křivky cyklického zpevnění/změkčení, cyklické deformační křivky, Coffinovy–Mansonovy a Wöhlerovi křivky. Hysterezní smyčky byly detailně analyzovány. • Pozorování mikrostruktury výchozího stavu pomocí TEM a porovnání s mikrostrukturou po cyklickém zatížení. • Pozorování povrchového reliéfu, který vznik díky lokalizaci cyklické plastické deformace - byla odhalena místa iniciace únavových trhlin a byl analyzován mechanismus jejich vzniku. • Měření kinetiky únavových trhlin. Oxidická disperse značně zpevňuje materiály, redukuje cyklické změkčení a stabilizuje mikrostrukturu v celém rozsahu teplot. Byly nalezeny velké rozdíly v životnosti jednotlivých ocelí. Ty byly vysvětleny pomocí rozdílných mechanismů iniciace trhlin a jejich různou rychlostí.
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Characterization of oxide dispersion strengthened alloys prepared from various precursor materials
Dobrovolný, Tomáš ; Havlík, Petr (referee) ; Moravčík, Igor (advisor)
Submitted master’s thesis studies the influence of input precursors (powders) on the resulting properties of prepared steels. When manufactured using the mechanical alloying method, the input powders can have a significant effect on the resulting properties. The austenitic steel 15-15Ti (1.4970) was chosen as the prepared alloy, which is gradually beginning to find application in nuclear energy. In this work, two approaches were used to produce this steel powder, firstly the production of an alloy from the precursor powder of austenitic steel AISI 304L and secondly the alloy was produced only from pure elements. For each of these methods, two different milling conditions were chosen. Thus, a total of four mixtures of 15-15Ti austenitic steel powders were produced, which were sintered into bulk materials using the SPS method. Mechanical properties of sintered specimens were tested by a tensile test and a hardness measurement by Vickers hardness test. At the same time, microstructure analysis using SEM and phase composition analysis by XRD were performed, both for prepared powders and for sintered bulks.
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New compositions of advanced oxide dispersion steels based on rare earth elements
Pech, Filip ; Kuběna, Ivo (referee) ; Hadraba, Hynek (advisor)
The main objective of present diploma thesis is to prepare three different classes of steels, differing by their content of chromium: 9Cr, 14Cr, 17Cr steels and their oxide dispersion strengthened variants. Steels were prepared from atomic and pre-alloyed powders by the mechanical alloying and compacted by the spark plasma sintering method. Used strengthening elements were yttrium, which is most commonly used, and aluminium. Preparation of oxide dispersion was done in two ways: direct adding of yttria and alumina and inner oxidation of aluminium and yttrium. In the experimental part has been found, that it is possible to make oxide dispersion by both ways, but aluminium strengthened steel has to be prepared by inner oxidation to ensure fine oxide dispersion.
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Early Stages of Fatigue Damage of Steels for Fusion Energetics
Kuběna, Ivo ; Spätig, Philippe (referee) ; Lukáš, Petr (referee) ; Kruml, Tomáš (advisor)
Hlavním cílem této práce bylo vysvětlit únavové chování ocelí ODS Eurofer, 14Cr ODS feritické oceli vyráběné v CEA (Commissariat a l’énergie atomique, Saclay, France) a 14Cr ODS feritické oceli vyráběné v EPFL (École Polytechnique Fédérale de Laussane, Switzerland). Pokud to bylo možné byly získané výsledky porovnány s ocelí Eurofer 97. Tato práce je součástí široké spolupráce, která je zaměřena na vývoj konstrukčních materiálů pro fuzní reaktory. V průběhu práce byly provedeny následující experimenty: • Standardní únavové zkoušky za pokojové teploty, při 650 a při 750 , byly získány křivky cyklického zpevnění/změkčení, cyklické deformační křivky, Coffinovy–Mansonovy a Wöhlerovi křivky. Hysterezní smyčky byly detailně analyzovány. • Pozorování mikrostruktury výchozího stavu pomocí TEM a porovnání s mikrostrukturou po cyklickém zatížení. • Pozorování povrchového reliéfu, který vznik díky lokalizaci cyklické plastické deformace - byla odhalena místa iniciace únavových trhlin a byl analyzován mechanismus jejich vzniku. • Měření kinetiky únavových trhlin. Oxidická disperse značně zpevňuje materiály, redukuje cyklické změkčení a stabilizuje mikrostrukturu v celém rozsahu teplot. Byly nalezeny velké rozdíly v životnosti jednotlivých ocelí. Ty byly vysvětleny pomocí rozdílných mechanismů iniciace trhlin a jejich různou rychlostí.
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High-temperature embrittlement of 14%Cr ODS ferritic steel in liquid lead environment
Dohnalová, Eva ; Čelko, Ladislav (referee) ; Hadraba, Hynek (advisor)
The thesis deals with the high-temperature embrittlement of 14%Cr ODS ferritic steel in liquid lead environment. The 14%Cr ferritic ODS steel ODM401 manufactured by powder metallurgy technology was used as an experimental material. The effect of the long-term annealing, surface corrosion attack in the melt Pb and Pb-Bi on the microstructure and mechanical properties was described. The subsequent microstructural changes were evaluated by means of scanning electron microscopy and transmission electron microscopy The mechanical behaviour of the experimental material was proven by means of microhardness test, impact test and static tensile test. The fractographical evaluation of fracture surfaces were performed on all samples. The surface attack and outstanding microstructural ganges were found after the long-time exposition of the steel in Pb/Pb-Bi melts at temperature 550°C/1000h and 500°C/1000h respectively. The embrittlement of the steel after exposition in Pb/Pb-Bi melts was comparable to the embrittlement after high-temperature annealing of the steel at temperature 650°C/1000h.
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