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Effect of molybdenum content on phase transformations in binary Ti-Mo alloys
Valešová, Veronika ; Stráský, Josef (advisor) ; Janeček, Miloš (referee)
Title: Effect of molybdenum content on phase transformations in binary Ti-Mo alloys Author: Veronika Valešová Department: Department of Physics of Materials Supervisor: PhDr. RNDr. Josef Stráský, Ph.D., Department of Physics of Mate- rials Abstract: β titanium alloys are highly appreciated group of structural materials. They provide an extraordinary combination of strength, toughness and fatigue resistance. These alloys are used predominantly in aerospace sector, chemical industry and medical engineering. We have studied three binary titanium alloys: Ti-12Mo, Ti-15Mo and Ti-18Mo (wt %). Apart from low temperature hexagonal close packed α phase and high temperature base centered cubic β phase, a metastable ω phase can be also found in this type of alloys. The ω phase is created in a diffusionless process by shifting the planes in the β phase and affects both mechanical properties and the α phase precipitation. We have examined the phase transformations occurring in the studied alloys using both in-situ and ex-situ methods. Resistometry, dilatometry and differential scanning calorimetry were used as the indirect in-situ methods. For the ex-situ methods, scanning electron microscopy and microhardness measurement were used. Complex characterization of β metastable titanium alloys showed the formation of the...
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Influence of deformation on precipitation processes in commercial Al-based alloys with Sc,Zr-addition
Leibner, Michal ; Vlach, Martin (advisor) ; Cieslar, Miroslav (referee)
1 Abstract: Mechanical and thermal properties of Al-5.4wt.%Zn-3.1wt.%Mg-1.5wt.%Cu (AA- 7075), Al-5.2wt.%Zn-3.0wt.%Mg-1.4wt.%Cu-0.2wt.%Sc-0.1wt.%Zr (AA-7075-ScZr) and Al-2.93wt.%Mg-0.34wt.%Mn-0.33wt.%Si-0.22wt.%Fe-0.19wt.%Cr-0.24wt.%Sc-0.06wt.%Zr (AA-5754-ScZr) alloys in as-cast and cold-rolled states were studied by differential scanning calorimetry and microhardness measurements. The initial values of microhardness reflect an effect of cold-rolling. The Sc,Zr-addition caused a pronounced hardening during annealing above ~ 300 řC. An easier diffusion of Zn, Mg, Cu and Mn atoms along dislocations led to a precipitation of Zn,Mg,Cu-containing and Mn-containing particles at lower temperatures in comparison with the AA-7075(-ScZr) and AA-5754-ScZr alloy in the as-cast state, respectively. The Sc,Zr-addition does not significantly influence precipitation of the particles form the Al-Zn-Mg-Cu system.
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Study of intermetallic phases in cast duplex steel
Ponížil, Ondřej ; Foret, Rudolf (referee) ; Pacal, Bohumil (advisor)
This thesis deals with the study of intermetallic phases in cast duplex stainless steel ASTM A890 Grade 4A considering degradation of mechanical properties in the result of isothermal aging in the temperature of 700 °C and 595 °C. The period of aging in the temperature of 700 °C was ranging from 1 to 160 hours and in the temperature of 595 °C it was ranging from 24 to 245 hours. The study of microstructure after aging in the temperature of 700 °C has proved that the -phases, Laves phases, chromium carbides and chromium nitrides were excluded. The phase was observed after four hours of aging in the temperature of 700 °C in / interface for the first time. The transformation was performed by eutectoid mechanism according to the equation + 2. The Laves phase has been observed after 10 hours of aging in / interphase and later in the ferrite grain as well. Chromium carbides and nitrides have created a continuous contour along to the / and /2 interface. After the temperature of 595°C there have been observed a large amount of small precipitates in the structure. The precipitates have been extracted from some selected samples to carbon replica. Following analysis has confirmed the presence of chromium carbides, -phases and Laves phases. The deterioration of mechanical properties, caused by the influence of secondary phase exclusion, has been confirmed by the Vickers hardness test and impact test including fractography analysis of the fracture surface. The hardness has an increasing tendency while the impact strength has been significantly reduced.
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"Optimizing the Al casting heat treatment"
Ostrézí, Barbora ; Cileček, Jarmil (referee) ; Horáček, Milan (advisor)
This master’s thesis focuses on the heat treatment of the aluminium alloy AlSi7Mg0,6 and also investigates the effects of different coolants usage on its mechanical properties. First part is dedicated to the description of aluminium alloys, their chemical composition, behaviour and mechanical properties with particular attention to the Al-Si-Mg alloys. This part was followed by the summary of commonly used heat treatment of aluminium alloys. The third part is dedicated to the experiment. Castings and test specimens were wax casted at Alucast, s.r.o. company. After annealing, the samples were quickly cooled down in four different coolants and underwent tensile testing. Their mechanical properties (tensile strength, yield point and ductility) were evaluated as well as microstructure. In the last part, the achieved results are presented.
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Examination of the polymorphism of the gene ApoE
NOVOTNÁ, Tereza
Alzheimer´s disease (AD) belongs to the most frequent cause of dementia in the world. It is determined that it is about 65-75 % of all the dementias (Preiss, Přikryková Kučerová, 2006). The term Alzheimer Dementia, as well as Pre-senile Form (AD) is used with the patients at the age up to 65 years (Seidl, 2015). After the age of 65 years we use the term Senile Dementia of the Alzheimer Type. (SDAT). Up to the age of 45 this desease is rare (Seidl, Obenberger, 2004). Causal treatment of this disease does not exist, because etiopathogenesis of the disease is not entirely clarified (Seidl, 2015). The aim of this bachelor´s work was to write a professional search to the given topic. In this theoretical part there is summed up the information about neurodegenerative disease, about dementia and (AD). Most importantly there are described the symptoms, the causes, phase, treatment, diagnostics and genetic disposition of AD. The description of polymerase chain reaction (PCR) and reverse hybridization on strips is also an important part of this theoretical part. In the practical part, the main goal was to master molecular biological methods. To achieve the goals and to get the best results, I chose two methods. In addition to optimizing the PCR ARMS method, reverse hybridization was used on strips. The above-mentioned second method was performed using the commercially available ApoE StripAssay? kit from ViennaLab. In this part of the paper are described all the procedures by which I achieved the results. Molecular biological methods were performed in a laboratory at the Health and Social Faculty of the University of South Bohemia in České Budějovice.
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Influence of heat treatment on deformation behaviour of wrought Mg-Zn-based alloys
Olejňák, Juraj ; Drozdenko, Daria (advisor) ; Mathis, Kristián (referee)
Title: Influence of heat treatment on deformation behaviour of wrought Mg-Zn alloys Author: Juraj Olejňák Department: Department of Physics of Materials Supervisor: RNDr. Mgr. Daria Drozdenko, Ph.D. Abstract: The aim of the present thesis is to understand an influence of heat treatment on microstructure and mechanical properties of extruded Mg-Zn based alloys containing an addition of Ca and Nd. Microstructural analysis provided by electron microscopy gave us information about homogeneity and distribution of precipitates in investigated Mg alloys after extrusion and a subsequent heat treatment. Microhardness and compression test along the extrusion direction have been performed to determine optimal aging conditions for achieving better mechanical properties, such as hardness and strength. The acoustic emmision technique was used to follow active deformation mechanisms during plastic deformation. Application of the acquired knowledge in material research can contribute to design novel Mg alloys with enhanced mechanical properties for specific applications. Keywords: magnesium alloys, isothermal aging, precipitation, mechanical properties
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Mechanical properties of pre-compressed Mg-Zn-Ca alloy
Hegedüs, Marius ; Dobroň, Patrik (advisor) ; Lukáč, Pavel (referee)
In wrought Mg alloys, their hexagonal closed packed structure together with a pronounced basal texture lead to anisotropy of mechanical properties. This bachelor thesis is focused on understanding the influence of previous deformation with further relaxation and/or additional heat treatment on deformation behaviour of the extruded Mg-Zn-Ca alloy. The significant influence of twins formed after pre-compression on mechanical properties was investigated. Evolution of microstructure, especially a formation of twins, is observed by light and scanning electron microscopy. The acoustic emission technique is used to determine active deformation mechanisms: dislocation slip and twinning. The results can be used for developing Mg alloys with enhanced properties.
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Microstructure and properties of enhanced twin-roll cast aluminium alloys.
Poková, Michaela ; Cieslar, Miroslav (advisor) ; Karlík, Miroslav (referee) ; Kruml, Tomáš (referee)
Three aluminium alloys from AA3003 series modified by zirconium were pre- pared by twin-roll casting. The role of composition, heat treatment and deforma- tion by cold-rolling or equal channel angular pressing on evolution of microstruc- ture and mechanical properties were studied. High density of α-Al(Mn,Fe)Si pre- cipitates formed during annealing between 300 ◦ C and 500 ◦ C. Coherent Al3Zr particles precipitated during annealing at 450 ◦ C with slow heating rate. Recrys- tallization resistance of deformed alloys was enhanced by either Al3Zr precipitates formed before deformation or by α-Al(Mn,Fe)Si particles nucleating simultane- ously with recrystallization. 1
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Phase transformations in Mg-Gd alloys
Stíbal, Adam ; Vlach, Martin (advisor) ; Mathis, Kristián (referee)
ývoj hořčíkový h slitin má ekonomi koEekologi ké opodst-tněníF yužití tě hto slitin je n- vzestupné tenden i - z-s-huje zejmén- do tr-nsportního pr·mysluD -le svoje upl-tnění n- hází i v medi íněF tedn- z metod zlepšení vl-stností hořčíku je legování jinými prvkyF vláš¡' do rý h výsledk· dos-huje legování prvky vzá ný h zeminF "ento typ slitinD kde legují ím prvkem je g-doliniumD jsou studovány v předklád-né prá i ve tře h tl-kově litý h slitiná h do kon entr- e IS hmF7F ředmětem prá e ylo studium fázový h tr-nsforE m- í při žíhání m-teriálu pomo í metody diferenční skenov- í k-lorimetrie při neizotermi kém žíháníF fyly pozorovány tři pro íh-jí í pro esy - spočteny jeE ji h -ktiv-ční energieF "ěmto pro es·m ylo n- zákl-dě srovnání s liter-turou přiř-zeno kl-strování -tom· qd - pre ipit- e met-st- ilní h fází β - β F I
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Positron annihilation study of precipitation effects in Mg-Tb alloy
Hruška, Petr ; Čížek, Jakub (advisor) ; Vlach, Martin (referee)
Magnesium alloys are currently widely used in industry as a modern material. Magnesium based alloys with rare earth elements shows very promising mechanical properties. In the present work the precipitation effects and the deve- lopment of microstructure of the Mg13Tb alloy (containing 13 wt.% of terbium) during isochronal annealing were studied by positron annihilation spectroscopy, microhardness measurement and differential scanning calorimetry. According to the results the creation of the precipitates β′′ , β′ and β in the studied alloy was observed and activation energies of these precipitates were determined by the Kissinger method. By microhardness measurement the natural ageing at room temperature of the Mg13Tb alloy was observed and described. 1
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