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Oxidation behavior adjustment for TiAl intermetallics by Al-Y multilayers
Handrk, Jiří ; Tkachenko, Serhii (referee) ; Jan, Vít (advisor)
Mechanické vlasnosti intermetalika na bázi titan hliník Ti-46Al-7Nb-0.7Cr-0.1Si-0.2Ni jsou konstatní do teploty 700 °C. Nad touto teplotou slitina oxiduje. Cílem této práce bylo zlepšit oxidační vlastnosti pomocí kovové multivrstvy na bázi yttrium hlinik. Pro depozici vrstev byla použita metoda PVD. Na vzorky byly naneseny vrstvy čistého ytria nebo kombinace yttrium, hliník. Vzorky byly následně žíhány v inertní atmosféře na 700°C a 900°C nebo nebyly. Kvalita nanesených vrstev byla zkoumána pomocí scratch testu a EDS analýzi. Dále byly vzorky izotermicky oxidovány na 900°C po dobu 100 hodin. Na vzorcích byly po oxidaci prováděny měření pevnosti v tříbodovém obybu a měření hmotnosti. Chemické složení oxidické vrstvy bylo vyhodnoceno pomocí EDS. Žádná z vrstev s nebo bez žíhání neprokázaly zlepšení oxidických vlastností. Vyšší teplota žíhání prokýzala zlepšení mechanických vlastnotí vrstvy, ale zhoršení materiálu.
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Preparation of ultra sharp tips for STM TERS applications
Šilhan, Lukáš ; Man, Ondřej (referee) ; Jan, Vít (advisor)
The goal of this bachelor thesis is preparation of Au tips by electrochemical etching. The theoretical part deals with comparison of microscopy techniques for materials surface characterization and Raman spectroscopy. The experimental part is focused on the settings of optimal etching parametres to gain appropriate geometry of fabricated tips. Function of tips is verified by evaluation of data gained by experimental measuring with this tips. Prepared tips are suitable for applications such as STM and TERS.
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Micro and nanocomposites in the microstructure of metallic materials
Olivo, Tomas ; Adam, Ondřej (referee) ; Jan, Vít (advisor)
This bachelor thesis focuses on the field of metal matrix nanocomposites. Firstly, the research covers the general mechanical characteristics of materials utilized in nanocomposites. Subsequently, the research defines the mentioned matrix and its different types, that are regularly applied during the production of nanocomposites. Secondly, the research analyses the types of reinforcing (strengthening) components and their use in matrix advancement. This will further lead to introducing the individual mechanisms that reinforce nanocomposites. Thirdly, this research describes the methods employed in the production of nanocomposites – both continuously or discontinuously reinforced. Moreover, the focus shifts to the individual types of materials that satisfy the required characteristics of composites. This outlines the specific types of composites created by the reactions within the materials. Finally, the research summarises the benefits of using nanocomposites.
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Oxidation barriers prepared by electrochemical procedures
Šťastná, Eva ; Pouchlý, Václav (referee) ; Jan, Vít (advisor)
A process with aim to prepare an oxidically and thermal resistant layer was performed on the samples from clear aluminium (99,99+ %, VÚK čisté kovy, s. r. o.) and on the samples from clear titanium (99,95 % Goodfellow) with a layer from sputtered aluminium (99,99 %, VÚK čisté kovy, s. r. o.), An oxidic layer was prepared on the samples by anodization in the oxalic acid. The layer had fine, hexagonally organized pores with the diameter of 30 nm. During the following processing was the structure prepared for the electrochemical deposition of copper to the pores. The aim of the electrodeposition was preparation of copper nanowires deposited into the pores of the oxidic layer. The process was performed in the solution of copper sulfate and sulfuric acid in water. The controlling parameter of the deposition was voltage which had a very asymmetric period. The period had to be optimized for a successful preparation of the wires. The result of the whole process was structure with oxidic matrix whose most of the pores were filled with copper.
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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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Influence of heat treatment on microstructure of iron alloys with carbon
Hranický, Pavel ; Jan, Vít (referee) ; Čupera, Jan (advisor)
The work focuses on the influence of hardening on the structure of specially prepared iron alloys with carbon, with as little admixture of other elements. The effect of hardening is judged by the hardness of the resulting alloy. Two hardening temperatures, one optimal for the hardness of the resulting structure and one high, are used. Hardening takes place in water. Four different alloys are examined for which the carbon content ranges from 0.01 % to 3.00 %. The results are evaluated on the basis of hardness, microhardness and observation of the resulting structures and phases on the light and electron microscopy. Part of the thesis is a review summarizing the knowledge about the heat treatment of iron alloys with an emphasis on hardening.
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Structure and properties of welded joint TiAl6V4 / 6061 made by electron beam technology
Král, Michael ; Jan, Vít (referee) ; Foret, Rudolf (advisor)
Titanium and aluminium alloys are among the most used construct materials due to their physical and mechanical properties except steels. The joining of these alloys can improve properties of whole construction but it is still difficult task. Especially welding of titanium and aluminium alloys is difficult cause formation of undesirable intermetalic phases in the weld. This thesis focuses on influences of electron beam welding parameters especially focusing and deflection of beam and preheating of base material to quality of heterogeneous join of titanium alloy Ti6Al4V and aluminium alloy EN AW-6061 – T651. There is described preparation of welded joins and brazed joins in the thesis, which are evaluated by light microscopy, scanning electron microscopy and EDS analysis of chemical composition. There was evaluated presence and chemical composition of formated intermetalic phases in the welded joins and quality and defects in the brazed joins.
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The use of surface modification for enhancing mechanical properties of SLM bulk materials
Barinka, Michal ; Řehořek, Lukáš (referee) ; Jan, Vít (advisor)
This diploma thesis deals with the surface modification of 3D printed metallic materials. The research part presents the most used methods of additive manufacturing and their process parameters influencing the quality of printed components. Defects arising during these processes and the techniques used to eliminate them are also described. In the experimental part of the work, the optimization of electrochemical polishing parameters was performed. The aim was to modify the rough surface of the components and thus prevent the formation of defects on the surface. The mechanical properties were investigated by means of three-point bending under static and dynamic loading. Fractographic analysis was performed on the quarry surfaces.
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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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Bulk materials from oxidized powder feedstock
Luptáková, Diana ; Molliková, Eva (referee) ; Jan, Vít (advisor)
In this thesis, methods of effective aluminium powder oxidation are evaluated, such as oxidation at higher temperatures in atmosphere, anodic oxidation and oxidation during high-energy ball milling. It describes following treatment and methods creating volume sammples in such way, where ductile properties are preserved, but the process of hardening by aluminium oxide occurs.
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