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Transparent YAG ceramics
Nowak, Ondřej ; Šťastný, Přemysl (referee) ; Trunec, Martin (advisor)
In this bachelor thesis was done basic theoretical analysis of problems regarding transparent ceramics, their preparation and aplications. Transparent YAG ceramics was prepared with 2 methods, cold isostatic pressing (CIP) and gelcasting (GC). Green bodies were prepared with CIP at pressure 700 MPa and 1000 MPa from 2 different slurries with 2 different Al2O3 powders and 1 prepared with gelcasting method. After that green bodies were annealed to remove binderes and vacuum sintered (10-3 Pa). Sintered samples were compared based on optical properties and microstructure. Because of better optical properties, microstructure analysis was done only on sampled pressed to 1000MPa and gelcasted. In both pressed samples high level of porosity was reported, one was almost completely non-transparent, the other was ranslucent. Sample prepared by gelcasting was almost clearly transparent, but due to presence of unreacted phase Y2O3, minor scattering of light passing through the sample was observed.
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Effect of material thickness on the width and properties of the heat-affected zone
Horák, Tomáš ; Slováček, Marek (referee) ; Kubíček, Jaroslav (advisor)
Thess deals with the welding of high-strength steel by the MAG method and the evaluation of structural and dimensional changes depending on the thickness of the material. CREUSABRO 4800 steel was chosen using MEGAFILL 742 M additive material. A weld was created with welding parameters of 130 A, 20.7 V and a feed speed of 35 cm/min with a swing of 7 m, on steel with a thickness of 3, 6, 10 mm. Subsequently, a weld was made on samples with a thickness of 10 mm with welding parameters of 300 A, 28.8 V, 35 cm/min with a swing of 7 mm, while one of the samples was preheated to the recommended temperature. The resulting macro structure, micro images and the thermally affected area were evaluated.
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Modification of the crystallographic texture of austenitic steel by 3D printing
Fábry, Adam ; Dočekalová, Kateřina (referee) ; Koutný, Daniel (advisor)
The microstructure, and therefore the mechanical properties of the material, depend on the cooling rate and the direction of the temperature gradient during cooling, which can be easily influenced in additively manufactured metal parts. In previous research, this change has been achieved by altering the scanning strategy during production. This work focuses on modifying the crystallographic structure of material X30Mn22 by varying the laser speed and power while maintaining a constant meander scanning strategy without rotation. To determine the applicable production parameters, a test of simple welds was conducted, providing a basis for future production and testing of bulk samples. The suitability of the production parameters and the microstructure achieved in the sample cross-section were evaluated using porosity on the fabricated bulk samples, and the microstructure was depicted using EBSD maps, showing significant changes in microstructure solely by altering the laser production parameters. Tensile samples were further fabricated for selected microstructure samples, and their mechanical properties were tested. The results of tensile tests showed differences between individual microstructures of 18% for yield strength and up to 10% for ultimate tensile strength. However, the most significant difference was in the achieved tensile modulus, which differed by up to 27%. The work provides fundamental insights into modifying and adjusting the structure of manganese-rich material by changing laser power and speed settings.
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Friction of Titanium Surfaces in Implantology
Heto, Matyáš ; Odehnal, Lukáš (referee) ; Ranuša, Matúš (advisor)
This bachelor thesis focuses on the frictional properties and wear resistance of Ti6Al4V alloy. This alloy is suitable for use in orthopaedic implants such as the first metatarsophalangeal (MTP) joint in the big toe. The aim is to investigate different surface treatment methods that can reduce friction and wear of this material. The effect of applying DLC coatings and creating microtextures or microstructures on the surface is described. Metal on metal pair tests have been carried out using profilometer and tribometer in pin on plate configuration. The results show a noticeably higher coefficient of friction for the Ti6Al4V alloy than for the compared CoCrMo alloy. DLC coating significantly helped in reducing the friction and wear of Ti6Al4V. This cannot be said for the two microstructures tested, which did not have a significant effect on the observed tribological properties. The results indicate the importance of surface treatment of Ti6Al4V alloy for use in implants.
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3D microstructure evaluation of developed Si3N4 material for alloyed wire rolling applications
Lövy, Vít ; Salamon, David (referee) ; Chlup, Zdeněk (advisor)
This diploma thesis is devoted to the use of 3D reconstruction using EBSD method for microstructural analysis of silicon nitride ceramic material predetermined for the rolling-mill used in the wire production. Application of this method can be used for the grain structure reconstruction and basic microstructural parameters can be than extracted. The development of a suitable method for 3D reconstruction of the structure of the materials the main aim of this work. There are described the different steps begun by sample preparation from the investigated material trough the optimisation of analysis parameters up to the visualization of the grain structure. New type of sample geometry has been designed which leads to the better and faster observation of the microstructure of ceramic materials. This thesis also describes optimal reconstruction parameters such as the geometry of the assembly used in the microscope without mechanical movement of the sample or the influence of conductive coating prepared via in-situ sputtering of suitable metal, or adjustment of the electron and ion beams. Further are described two options of software which can be used for the final generation of 3D structure information and are assessed their advantages and disadvantages. The effect of the filter setting and other parameters and their influence on the resulting structural parameters are also evaluated.
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Structural analysis of austenitic weld joints
Procházka, Robert ; Foret, Rudolf (referee) ; Havlík, Petr (advisor)
The bachelor thesis deals with structural analysis of austenitic weld joints by using methods of material science. The theoretical part of the thesis summarizes the problematics of welding of high-alloy steels. After the general definition of welding and weldability of high-alloy steels, the thesis focuses on structural adjustments including welding defects during the welding process. Selected methods of fusion welding that were used to create these welds are mentioned in the second half of the theoretical part. The experimental part covers the structural analysis of the welds, which consists of microstructure evaluation, chemical composition analysis, and microhardness test.
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Immiscible alloy based on Fe-Cu system
Semerák, Petr ; Havlík, Petr (referee) ; Jan, Vít (advisor)
The aim of this work is the preparation of FeCuMn alloy in equimolar composition by melting and the analysis of the resulting microstructure. The theoretical part of the work deals with miscibility and the use of immiscible systems in practical applications. Furthermore, the influence of cooling rate and the effect of the ratio of the components of the immiscible Fe-Cu system on the resulting microstructure are described. The practical part of the work presents the microstructure of FeCuMn alloy, which was prepared by melting in an induction furnace under a protective atmosphere of argon. Furthermore, the practical part deals with the chemical composition of the individual phases and the shape of the resulting phases. For the FeCuMn alloy, the melting temperature of the phases is analysed, the material is also deformed, and the hardness of the deformed and undeformed material is evaluated. In the subsequent discussion, the results from the experimental part are related to published experimental results by other authors.
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Welding technology of turbine rotors
Pivoňka, Vít ; Kubíček, Jaroslav (referee) ; Daněk, Ladislav (advisor)
The paper deals with all the possibilities which can be used to weld the rotors of turbines, both the root and the filler welding. All these methods are thoroughly analyzed and their properties are described, especially the size of the heat input by welding of rotors of turbines. Further in this work is described the organization of the structure by means of a metallographic survey and a test of welds and materials, which are performed to check whether the material and the welding method are suitable for welding of rotors of turbines. In the experimental part are described all welds made by different welding parameters, one of these welds is chosen to achieve the best welding of the weld root. This weld is further investigated for hardness and change of microstructure after welding.
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Influence of the electron beam trajectory on the surface properties of steel 42CrMo4
Mikuš, Tomáš ; Kouřil, Miloslav (referee) ; Foret, Rudolf (advisor)
The thesis deals with surface quenching of steel 42CrMo4 by electron beam. Influence of technologic parameters and beam deflection on properties and structure of prepared layers is studied. Electron beam surface quenching was applicated with and without melting of the surface. Structures of layers made by electron beam quenching were compared with structures made by laser and electromagnetic induction. Structures and phases were analysed by optical microscopy, SEM and roentgen diffraction. Hardness was measured on hardened layers.
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Physical Phenomenon as a Creative Method in Architecture
Buryová, Tereza ; Mach, Jan (referee) ; Kristek,, Jan (advisor)
Cellular_ polar research station Antarctica is the driest, the busiest and most extensive place on Earth, half-year-shrouded. People still live here. They set up the research stations in which they live and work. In these extreme climatic conditions, the station originates and disappears due to natural behaving. Stations provide researchers with safety and space for research, including comfort. They are built in different ways and provide different comforts, according to technological and transport options.
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