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Microstructure and properties of Al-Li based alloys
Belejová, Sára ; Cieslar, Miroslav (advisor) ; Málek, Přemysl (referee)
This bachelor thesis is devoted to a study of rapidly solidified metallic strips prepared from two Al-Li-based alloys of the third generation. The aim of the thesis is to provide initial information about this new class of materials that could find application in aerospace industry. Al-Li third-generation alloys differ from previous generations by a lower Li content and thus by a type of main reinforcing phases. However, since conven- tional processings have already exhausted their possibilities that would significantly im- prove mechanical properties of these alloys, less traditional methods are tested, including rapid solidification processing by a melt-spinning method. These materials can achieve exceptional properties after milling and compactization thanks to finer microstructure and higher supersaturation of the solid solution. LOM, TEM (STEM) observations, and EDX analyses were used for the examination of the microstructure. In-situ resistometric measurements and in-situ TEM heating were performed to investigate the phase transi- tions. The structure of the alloys changes during heating. Grains of both alloys do not contain large particles after annealing. Only newly-formed coarse particles were observed on grain boundaries. The added scandium and zirconium resulted in a formation of a fine...
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Transmission Electron Microscopy of Al-Mg Aluminium Alloys with Addition of Sc and Zr
Křivská, Barbora ; Šlapáková, Michaela (advisor) ; Málek, Přemysl (referee)
Abstract. The microstructure and its evolution during isochronal annealing of a twin roll cast Al-3.2Mg-0.19Sc-0.14Zr (wt.%) alloy was investigated by light optical microscopy and electron microscopy. Two procedures - equal channel an- gular pressing and annealing at 300 řC for 8 h were applied to enhance mechanical properties of the alloy. The annealing led to the precipitation of a fine dispersion of Al3(Sc,Zr) particles providing an increase of ∼20 HV in the Vickers microhard- ness. Equal channel angular pressing refined significantly the microstructure and raised the microhardness by about 30 HV. Applying of the 300 řC / 8 h both before and after equal channel angular pressing did not induce further strength- ening. However, the precipitation of the Al3(Sc,Zr) phase had a stabilizing effect when the material was exposed to the subsequent isochronal annealing. 1
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The investigation of an Al-Zr-Ti alloy prepared by spark plasma sintering of atomized powder
Molnárová, O. ; Málek, P. ; Lukáč, František ; Chráska, Tomáš ; Cinert, Jakub
The microstructure and mechanical properties of a powder metallurgical Al-Zr-Ti alloy was studied. Fine powder with a typical size below 50 ?m was prepared by gas atomization. The smallest powder particles with a diameter below 10 ?m exhibited a segregation free microstructure. Larger droplets were found to contain intermetallic particles rich in Zr and Ti. The gas atomized powder was consolidated by spark plasma sintering (SPS) at various temperatures ranging from 450 to 550 °C. During SPS the materials microstructure remained nearly unchanged and a fine grain size between 2 and 3 ?m was observed. All SPS samples exhibited a microhardness of around 90 HV. The annealing (1 h, 500 °C) of the sample sintered at the highest temperature (550 °C) resulted in a decrease of microhardness to 75 HV as a result of changes in the phase composition, the fine grain size was retained. Natural aging at room temperature was not observed.
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Advanced aluminium alloys prepared by powder metallurgy and spark plasma sintering
Molnárová, Orsolya ; Málek, Přemysl (advisor) ; Haušild, Petr (referee) ; Vojtěch, Dalibor (referee)
Mechanical properties of aluminium alloys highly depend on their phase composition and microstructure. High strength can be achieved among others by introduction of a high volume fraction of fine, homogeneously distributed second phase particles and by a refinement of the grain size. Powder metallurgy allows to prepare fine grained materials with increased solid solubility which are favourable precursors for further precipitation strengthening. Gas atomization was used for the preparation of powders of the commercial Al7075 alloy and its modification containing 1 wt% Zr. A part of gas atomized powders was mechanically milled at different conditions. Mechanical milling reduced the grain size down to the nano-size range and the corresponding microhardness exceeded the value of 300 HV. Powders were consolidated by the spark plasma sintering method to nearly fully dense compacts. Due to a short time and relatively low temperature of sintering the favourable microstructure can be preserved in the bulk material. The grain size of compacts prepared from milled powder was retained in the submicrocrystalline range and the microhardness close to 200 HV exceeded that of the specially heat treated ingot metallurgical counterparts. The prepared compacts retained their fine grained structure and high...
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Flow Measurement - oriffice plates
Krátká, Lucie ; Málek, Petr (referee) ; Šedivá, Soňa (advisor)
The aim of the Bachelor thesis is to approximate the fluid flow measurement using differential pressure transducers inserted into fully filled circular cross-section conduits running full in the industrial sector. The introduction of the Bachelor thesis describes and explains the principle of fluid flow measurement using differential pressure transducers and the basic types of primary flow elements. Practical part consists of the design of practical calculations of individual parameters of standardized orifice plates, the design of a program for calculation of these parameters, comparing the achieved results with the output from the program Conval, evaluating these results and analyzing the measurement uncertainties for the parameters that affect the design of the standard orifice plate.
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Superplastic deformation of ultrafine-grained magnesium alloys with potential for use in medicine
Vávra, Tomáš ; Minárik, Peter (advisor) ; Málek, Přemysl (referee)
Mechanical properties of ultra-fine grain magnesium alloys AE42 and LAE442 prepared by ECAP were investigated. The study was focused on finding suitable conditions for the superplastic deformation. In the first place, the thermal stability of the microstructure was investigated. Afterwards, the strain rate sensitivity was measured in the temperature range 180-240 řC and the strain rate of =5·10-5 -2·10-3 s-1 . Conditions for tensile tests of =10-4 s-1 at 180 ř C and =10-3 s-1 at 240 řC ware selected. Finally, the microstructure change as a result of deformation was observed by AFM and EBSD. The results were discussed with mechanical tests. The best superplastic properties were observed in LAE442 alloy deformed at 180 ř C and =10-4 s-1 . Under these conditions, the achieved tensile strain was 395%.
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Interpretation of the novel Spas by Ivan Matoušek
Malá, Lucie ; Vojtěch, Daniel (advisor) ; Málek, Petr (referee)
The master thesis discusses the novel Spas by Ivan Matoušek published in 2001. The description of the structure and narrative time of the novel is followed by a characterization of the ironic self-conscious narrator and his relationship to the fictional world and the main character. The interpretation is partly inspired by a theoretical paper on irony by Vladimir Jankélévitch, which is compared with Paul de Man's concept of irony. The thesis also refers to Linda Hutcheon's theory of self- reflexivity and metafiction and employs the concept of mise en abyme.
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Comparison of Shifts in the Intersemiotic and Interlingual Translation of Leaving by Václav Havel.
Korábová, Zuzana ; Špirk, Jaroslav (advisor) ; Málek, Petr (referee)
The central focus of this Master's thesis is to describe, explain and classify intersemiotic translation within current translation studies. Given the interdisciplinary nature of the thesis, the theoretical part draws inspiration also from aesthetics, semiotics, adaptation, literary and film studies. Our findings are applied to the empirical material - interlingual and intersemiotic translation of Leaving by Václav Havel. Both translations are thoroughly analysed and the identified shifts are classified into categories primarily inspired by Anton Popovič's model of translation (1975, 1983). Comparison proved that the approach to intersemiotic translations/film adaptations as interlingual translation works. Although, there was a need to create new categories for some shifts in the film adaptation. Based on that, we propose a new model of intersemiotic translation, which could serve as inspiration for further research.
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Philosophical aspects in Josef Čapek's work
Pulcová, Tereza ; Vojtěch, Daniel (advisor) ; Málek, Petr (referee)
This bachelor thesis, divided into two parts, is focused on Josef Čapek's later literary work. The main objective of the first part is the interpretation of philosophical aspects in Kulhavý poutník (attention is focused especially on the specific genre and on the principle of Čapek's thinking), the second part is based on philosophy of existence, particularly on Karl Jaspers' philosophical work, and its aimed to some items which are common for both authors (e. g. the modern situation comprehension or the conception of death).
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