National Repository of Grey Literature 20 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Production of aluminum castings using metal inserts in the technology of casting into ceramic shells
Straka, Pavel ; Zemčík, Ladislav (referee) ; Krutiš, Vladimír (advisor)
The thesis is focused on manufacturing of aluminium castings with inserts by the hybrid investment casting technology. Three measures were proposed to avoid shell cracking caused by thermal expansion of insert. It seems that the covering of insert with a wax is the most efective solution, becasue after dewaxing a gap is formed, which allows insert to dilate. The other solution was based on change of molochite sand to quartz, which has a higher thermal expansion. The last mean to prevent the shell from cracking was adjustment of dewaxing cycle from shock to gradual. Ceramic shell was heated from room temperature to 650 °C. This solution did not avoid shell cracking. Then the simulation of shell heating, pouring of metal and the solidification was made. The information obtained by the manufacturing of experimental casting was used to prototype casting of impeller.
Analysis of the Structure and Properties of Al-Si Alloy during Holding Time of the Melt
Krahula, Karel ; Lichý, Petr (referee) ; Kaňa, Václav (referee) ; Zemčík, Ladislav (advisor)
This thesis is dedicated to the production of aluminum casting alloys. It maps the course of changes in the morphology of eutectic and its influence on mechanical properties during the long-term meltdown. In particular, the use of image analysis methods contributes to describing these processes. The presented results show that the eutectic shape does not change even during the meltdown for 110 minutes. There is only a roughing and an increase in grain size. There was also no influence on the mechanical properties that fit the practical application of the alloy examined
Castings from TiAl alloys for the IC engines
Kašpar, Jan ; Záděra, Antonín (referee) ; Zemčík, Ladislav (advisor)
The bachelor tesis is focused on intermetalic alloys of TiAl. Analysis of microstructure including heat threatment and alloying. Next part is focused on melting and casting TiAl including safety of work and recyklation. Last chapter is developed to apllication mainly engine valves.
Castings from TiAl alloys for the turbochargers
Kudýn, David ; Malec, Silvestr (referee) ; Zemčík, Ladislav (advisor)
The bachelor thesis is focused on the analysis of intermetallic alloys TiAl. First of all, it is analysed their properties and the way how they change depends on their treatment and influencing of alloying elements. Then ways of utilization in practice are stated here. Attention is concentrated especially on turbochargers wheel and their comparison to convention materials. After that individual options of melting and casting and materials for melting crucibles and moulds associated with them are there discussed. In the end, the thesis has analysed the ways of recycling of residual material.
Control over grain size and morphology of eutectics of Al - Si alloys
Malatin, Richard ; Krahula, Karel (referee) ; Zemčík, Ladislav (advisor)
This work will be focused on problematics of controling the grain size and morphology of eutectics of Al-Si alloys intended for casting. The main content of this work is to understeand the mechanism of crystallization and formation of eutectic in aluminium based alloys with overview of actual trends in solving the issue.
Survey of applications of investment casting from ferrous alloys and super-alloys
Smilovský, David ; Zemčík, Ladislav (referee) ; Horáček, Milan (advisor)
A content of this thesis is a survey of casting applications from specific alloys manufactured by investment casting. Thesis shows basic principles of investment casting method, its possibilities and advantages. It also lists a short metallurgical description of ferrous alloys a superalloys cast by this method. The main aim is on specific industrial branches, where these precise castings are used. There are specific applications of parts presented from various Czech and foreign foundries.
Directional solidification of the combustion turbine blades
Jeřábek, Petr ; Blažík, Petr (referee) ; Zemčík, Ladislav (advisor)
This thesis summarizes knowledge about directional solidification of nickel based superalloys in the process of production of gas turbine blades. It focuses on material and metallurgical properties of nickel based superalloys, directional solidification and advantages of usage of this process in production of gas turbine blades.
Decarburization of austenitic steels and its influence on material properties
Vítek, Radovan ; Zemčík, Ladislav (referee) ; Šenberger, Jaroslav (advisor)
This master´s thesis deals with theoretical study of decarburization of austenitic steels. Mathematical model, which analyse numerical calculations, was compared with experiments. Obtained results were discussed considering validity of model and performed aproximations.
Application of Homogenization Annealing to Suppress Silicon and Nickel Segregation in Ductile Iron
Pavloušková, Zina ; Zemčík, Ladislav (referee) ; Vřešťál, Jan (referee) ; Švejcar, Jiří (advisor)
This doctoral thesis deals with the comparison of different methods of alloying elements’ concentration measurement based on energy dispersive spectroscopy and also with the suitability of particular methods of quantitative assessment of heterogeneity of the spheroidal graphite cast iron matrix. The segregation curves construction, distribution coefficient and heterogeneity index formulation is also discussed. The notion “normalized distribution coefficient” is introduced newly. The goal of the thesis, which is to be achieved by means of evaluation of large experimental data sets, is the evaluation of applicability of homogenization annealing of spheroidal graphite cast iron with the aim to eliminate segregation of silicon, and mainly nickel, as pearlite- and carbide-forming agent at the border of an eutectic cell. The result is an optimized homogenization annealing schedule maximizing the suppression of silicon and nickel segregation while taking into account the minimization of financial expenses and risk of grain coarsening.
Processing of Nb-containing TiAl intermetallics and its Physical and Chemical Aspects
Barták, Tomáš ; Dlouhý, Ivo (referee) ; Zemčík, Ladislav (referee) ; Dlouhý, Antonín (advisor)
Prezentovaná práce se zabývá vakuovým indukčním tavením intermetalické slitiny Ti-46Al-7Nb (at. %) v žáruvzdorných kelímcích na bázi Y2O3. Byla provedena série taveb pro teploty přehřátí taveniny 1630, 1680 and 1730 C a při různých dobách výdrže na této teplotě v rozmezí 5 až 30 minut. Ze slitin ztuhlých v tavících kelímcích byly připraveny metalografické výbrusy, které sloužily k hodnocení mikrostruktury a vyhodnocení složení fází. Pro získání těchto dat byly použity metosy elektronové mirkoskopie SEM a EDS. Kvantitativní hodnocení mikrostruktury, zejména obsahu oxidické faze ve slitině, bylo provedeno pomocí software Adaptive Contrast Control (ACC). Analýza obsahu kyslíku ve ztuhlé slitině byla provedena metodou IGF (fúze v inertním plynu). V této práci jsou pochody na rozhraní slitina/oxidický kelímek posuzovány také z termodynamického hlediska a to s použitím aktivit jednotlivých složek v systému. Data prezentovaná v této práci mohou být použita pro nastavení a optimalizaci procesů tavení intermetalik TiAlNb.

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