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High temperature service embrittlement of EUROFER´97 steel
Stratil, Luděk ; Jan, Vít (referee) ; Hadraba, Hynek (advisor)
The thesis describes effect of long-time ageing on the microstructure and properties of the Eurofer´97 steel. The ferritic-martensitic reduced activation steel Eurofer´97 is candidate structural material for in-core components of proposed fusion reactors. Thesis is focused on examination and description of brittle-fracture behaviour of the steel. Properties of the steel were investigated in as-received state and state after long-time ageing. Detailed microstructure studies were carried out by means of optical and electron microscopy and also by means of quantitative electron microscopy. Mechanical properties were evaluated also in both states by means of hardness tetsing, tensile testing and Charpy impact testing. Fractography analysis of fracture surfaces was carried out on samples after Charpy impact testing.
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Structural Stability of Creep-Resistant Steels and their Weldmets
Šohaj, Pavel ; Jan, Vít (referee) ; Foret, Rudolf (advisor)
The structural stability of creep-resistant steels P22, P91 and Eurofer´97 and structural stability of weld joint P22/P91 have been studied. The microstructural changes during annealing at temperatures of 500 – 900°C were examined. The state of equilibrium have been simulated using the ThermoCalc software. The computed results were compared with published data. A good agreement between the simulation and the published data was observed.
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The material base of trial bicycles
Debs, Martin ; Hanusová, Petra (referee) ; Jan, Vít (advisor)
This bachelor thesis is focused on the material analysis of trial bicycle parts. The main aim is the summary of materials and technologies used in construction of these bicycles, exploiting knowledge of material microstructure theory, both in theoretical and practical sections of the thesis. To attain the aims, it was necessary to perform a proper metallographic specimen preparation. These specimens allowed to observe a material microstructure of various bicycle parts and demonstrate the use of metallographic techniques for determining the type of the used materials and applied processing technologies. Comprehensive metallographic analysis proved the use of materials in ordinary quality and ordinary technological processes. Subsequently we documented and explicated various defects in microstructure of the examined parts.
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The Pulse discharge welding applications and weld analysis
Kocák, Tibor ; Molliková, Eva (referee) ; Jan, Vít (advisor)
Theoretical part of this bachelor's thesis contains overview information about special welding technology, which uses capacitor discharging. Pracitcal part is about experimental attempts showing the application of the theory of welding using capacitor welder with specific settings, preparation and rating samples. Microstructure of the samples was evaluated by standard metallographic techniques.
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Reaction synthesis of bulk intermetallic materials in Ti Ni system form kinetic spraying deposits
Dyčka, Martin ; Moravčík, Igor (referee) ; Jan, Vít (advisor)
Bachelor’s thesis deals with intermetallic compounds which are formed in nickel-titanium binary system. The theoretical part of this thesis deals with the best known titanium based intermetallics, diffusion and possible processing technologies of intermetallic materials. In experimental part, a nickel-titanium coating created by cold spray technique was used. The changes in microstructure depending on annealing temperature were analysed. The results contain photographs of microstructure and fractures, values of microhardness and results of chemical analyses.
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Self-organized nanostructured oxide layers
Šťastná, Eva ; Pouchlý, Václav (referee) ; Jan, Vít (advisor)
Series of anodization experiments was conducted on pure aluminium (99,95 Goodfellow) substrates with the aim to map the possibilities and evaluate available techniques. Oxalic acid electrolyte was used for anodization at different voltage levels ranging from 20 to 60V, while current was always measured continuously during the experiment. The influence of substrate surface treatment, time and grain size of the substrate was documented for as anodized oxide structures using FEG-SEM. Well aligned and evenly distributed pores of the diameters ranging 20- 35 nm were achieved. Extremely fine pores down to 10 nm were achieved using the step-down technique governed by current limitation. Further post-anodizing treatment was evaluated – pore widening by chemical and electrochemical etching, which resulted in pores 80nm wide. The feasibility of electrodeposition of metallic wires directly into the AAO structure without substrate removal was evaluated. DC, AC symmetric and non-symmetric voltage setups were used. The deposition experiments results varied strongly depending on the post anodization treatment. For combination of pore-widening after anodizing with step-down stage, the deposition of copper nanowires was achieved. For simple step-down procedure, creation of very fine copper particles was realized using non-symmetric AC deposition. Further experiments and feasibility of metals electrodeposition in the AAO pores without substrate removal is discussed.
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Reaction synthesis of bulk Fe-Al intermetallic materials
Dyčková, Lucie ; Hutařová, Simona (referee) ; Jan, Vít (advisor)
Bachelor’s thesis deals with iron aluminides. In literature analysis are the best known and the most widely used intermetallics materials, diffusion and other possible processing technologies of intermetallic materials. In experimental part was used sprayed coating. This sprayed coating was produced by cold gas-dynamic spray. In this thesis were analysed changes in microstructure of iron aluminides depending on annealing temperature. This thesis contains photographs of microstructure and analyses from electron microscopy and measurement of microhardness.
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Optimization of heat treatement process for alloyed case hardenening steel
Roubalová, Jana ; Pantělejev, Libor (referee) ; Jan, Vít (advisor)
This bachelor’s thesis deals with the assessment of the influence of heat treatment on the microstructure and mechanical properties of medium alloyed steel 18CrNiMo7-6. The work contains assessment and further proposal of suitable austenitizing temperature for heat treatment. To select the optimal variants of heat treatment five different temperature modes were tested. The theoretical part describes the various methods of heat treatment, with a focus on medium alloyed steels. The practical part presents microstructure of the evaluated steel, its hardenability and hardness depending on the temperature regime of treatment.
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Oxidation barriers prepared by electrochemical procedures
Mengyan, Tomáš ; Man, Ondřej (referee) ; Jan, Vít (advisor)
The presented bachelor thesis deals theoretically with use of anodization procedures for preparation of self-organized porous oxide layers on aluminium. The techniques leading to different pore structures are summarized and the use of porous anodic alumina in various applications of nanotechnology are mentioned. The thesis is composed as initial entry-level theroretical study for prospective experimental work in the field of porous anodic alumina.
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Structure of Heat Resistant Steels
Skýba, Pavel ; Foret, Rudolf (referee) ; Jan, Vít (advisor)
This work is a compilation essay about structure of heat-resistant steels, creep, strengthening and heat treatment based on available literature sources. The main chapters of the work deal with creep deformation, its mechanisms and the ways of strengthening used in heat-resistant steels. Separate chapters deal specifically with precipitation strengthening, minority phases that can be found in heat-resistant steels and their heat treatment.
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