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Structure and Properties of Selected Magnesium Cast Alloys
Svozil, Libor ; Pacal, Bohumil (referee) ; Podrábský, Tomáš (advisor)
Microstructure and mechanical properties of AZ91 magnesium alloy after die cast (casting under pressure) and squeeze casting were comparated. The compare of incident phases, their microhardness, gas bubbles in the alloy, hardness and other mechanical properties of alloy are included in this work. For compare has been used a light microscopy, tensile test, hardness and microhardness measurements, image analysis and scaning electron microscopy.
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Evaluation of corrosion on selected aluminium alloys
Skýba, Pavel ; Tulka, Jaromír (referee) ; Pacal, Bohumil (advisor)
The thesis focuses on the corrosion research of AlCu4Mg1 aluminium alloys of square shape and sheet metal coated in 99.5% aluminium. The theoretical part deals with the characteristics of aluminium, the classification and naming of aluminium alloys and the impact of admixtures on aluminium alloys. In the following chapter a general introduction to metal corrosion, its differentiation according to the type of corrosion attack, mechanisms of corrosion, the impact of corrosive environment, according to the choice of anti-corrosion protection, etc. is given. The main part is devoted to the corrosion of aluminium with a special importance of the impact of admixtures on aluminium alloys, the types of corrosion attack, the impact of corrosive environment as well as of the anti-corrosion protection of aluminium alloys. The corrosion tests in controlled atmosphere are considered in the next chapter, while the last one deals with the evaluation methodology of the process of corrosion. At the beginning of the experimental part all the used samples and materials are introduced. The thesis continues then with an overview and a description of the methods used for experiments. The measurement procedure and the results of the experiments are presented in the following chapter that focuses on the metallographic analysis of the aluminium alloy samples before the experiment and after the corrosion attack. The main part of the chapter deals with the dependence of corrosion speed of the individual aluminium alloy samples on time after being exposed in the climate chamber and the salt fog chamber
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Structural-mechanical characteristics of the selected type of low-carbon steel after cold drawing and heat treatment
Stopka, Maroš ; Molliková, Eva (referee) ; Pacal, Bohumil (advisor)
This bachelor's thesis focuses on changes in the mechanical properties of low-carbon wire that has been cold-drawn and subsequently heat-treated. Mechanical tests, from which the values of elongation, yield strength and tensile strength were measured, were performed on all samples within 24 hours after they were collected. Two different production rates were established on the hot dip galvanizing line to achieve different time intervals of the annealing process. The experiment was performed at all stages of wire diameter reduction, including the input material. This work also includes metallographic analyzes of samples that have been both polished and etched. The most representative samples were selected for analysis. The results show that deformation caused changes in mechanical properties and an increase in strain hardening, which was subsequently removed by heat treatment.
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Phase Transformations during Heat Treatment of Fe - C Materials
Škvarka, Jakub ; Pacal, Bohumil (referee) ; Molliková, Eva (advisor)
The goal of this thesis is a study of heat treatment of iron-carbon alloys from a physical angle. Characteristics of main components from this system and their modifications are described there. There is also described what is going on during heat treatment especially from an angle of thermodynamics and kinetics, thanks to available information from literature. The knowledge is applied on specific types of heat treatment of material and processes which can follow it.
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Processing of Mg-based powder materials by SPS method
Moleková, Kristína ; Pacal, Bohumil (referee) ; Doležal, Pavel (advisor)
Diploma thesis occupy with preparation of porous material from magnesium powder with a HAp admixture by cold pressing followed by spark plasma sintering (SPS). This thesis contain both preparation of bulk material, diffusion plot and charakterization of materials based on the compaction process conditions. On the basis of physical mechanical characteristics, the impact of the pressing process on the subsequent sintering and the resulting material properties are evaluated. Bulk material is characterized considering to structure and physical–mechanical properties. Properties of final metarial will serve to optimize conditions for process of bulk material preparation.
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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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