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Protection of magneisum alloys
Ruttkayová, Veronika ; Wasserbauer, Jaromír (referee) ; Zmrzlý, Martin (advisor)
The aim of this bachelor thesis is to characterize the mechanical properties of protective coatings on magnesium alloy AZ91. In the introductory there are summarized the findings of magnesium, magnesium alloys, corrosion and protection against it. Important properties such as adhesion and hardness were tested by standardized tests. The result can be used to determine application fields of these coated alloys in practice.
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Tension - compression asymetry non-ferous alloys
Čavojec, Martin ; Judas, Jakub (referee) ; Zapletal, Josef (advisor)
Bakalářská práce se zabývá asymetrickou odezvou na tahové a tlakové zatěžování neželezných kovů, jmenovitě hořčíkových slitin. Popisuje základní problematiku zkoušek tahem a tlakem, experimentální stanovením asymetrické odezvy, vliv rozličných parametrů na asymetrickou odezvu na tahové a tlakové zatěžování, a také možný popis asymetrie jako funkci orientace a textury. Na závěr práce popisuje experimentální stanovení a vyhodnocení asymetrické odezvy na tlakové a tahové zatěžování hořčíkové slitiny AZ61, s metalografickou analýzu tyto slitiny.
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The numerical analysis of interactions between twins and precipitates in magnesium alloys
Bogdan, Miloš ; Gröger, Roman (referee) ; Šiška, Filip (advisor)
Hlavním cílem této práce je analýza napěťových polí, indukovaných dvojčatěním ovlivněných přítomností precipitátu před čelem dvojčete. Zvolený případ popisuje tahové dvojče {1012} 101 1 s lamelarními precipitáty v hořčíkové slitině AZ31. Systém je modelován metodou konečnýh prvků jako 2D elastická eliptická inkluze, se dvěmi elastickými precipitáty tyčovitého tvaru, nacházející se před čelem elipsy obklopené plastickou matricí modelovanou pomocí krystalové plasticity. Analýza dvojčat a precipitátů s různou tlouštkou ukazje inhibující účinek precipitátů na růst tloušťky dvojčat. Velikost tohoto účinku se mění s tloušťkou dvojčete v důsledku komplexní interakce mezi dvojčetem precipitátem a indukovanou plastickou zónou.
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Corrosion Resistance of Structural Magnesium Alloys
Tkacz, Jakub ; Pacal, Bohumil (referee) ; Hadzima, Branislav (referee) ; Havlica, Jaromír (advisor)
This thesis describes magnesium alloys, their properties and methods of their production. However, experimental part is focused on AZ91 magnesium alloy. Conversion coatings were prepared on the AZ91 surface – chromate coating, phosphate permanganate coating and fluoride coating. Corrosion resistance of the prepared coatings were compared by immersion tests and by potentiodynamic methods. Evaluation of corrosion resistance by immersion tests was successful only for phosphate permanganate coating. Only this coating was removed during cleaning of the samples. For comparison of corrosion resistance was important to find the correct procedures and optimize the measurements methods. For these purposes have been chosen galvanic zinc coating on steel sheets. Thickness of the zinc coating were 8 and 30 microns. This coatings provide uniform zinc surface without heterogenities which was important for the potentiodynamic measurements. After optimization methods for potentiodynamic measurements by galvanic zinc coatings have been measured magnesium alloy AZ91 uncoated and coated by conversion coatings. For uncoated AZ91 magnesium alloy was determined suitable method so called virgin cathodic curve. On the other hand, for the coated AZ91 magnesium alloys was determined suitable method so called combined curve, within which we measured cyclic voltammetry curve (± 5 mV) and then virgin anodic curve.
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Advanced Magnesium Alloys Surface Modification by Ni-P Based Coatings
Kosár, Petr ; Pacal, Bohumil (referee) ; Nový,, František (referee) ; Havlica, Jaromír (advisor)
The dissertation thesis deals with the modification of the surface of advanced magnesium alloys with Ni-P based coatings. At the beginning of the theoretical part, the structures of the used magnesium alloys and the influence of individual alloying elements on their properties are characterized. In the following part of the thesis the current knowledge in the field of electroless deposition on metal substrates is summarized. The theoretical part of the thesis is closed with contemporary research study in the field of clarification and determination of possible mechanism of electroless deposition. For the subsequent investigation of the mechanism of electroless deposition on magnesium alloys, it was necessary to characterize the microstructure and composition of individual magnesium alloys in the first phase of the experimental part. The exact composition of elements was determined using glow discharge optical emission spectroscopy and scanning electron microscopy with EDS was used for composition of phases of magnesium alloys. Using scanning electron microscopy and detailed elemental analysis of the coated magnesium substrate, it was found that for optimal Ni-P coating deposition on magnesium alloys, acid pickling prior coating is required in a mixture of acetic acid and sodium nitrate. Using the XPS method, it was found that the phosphorus atom in the sodium dihydride-diphosphate reducing agent has a + V charge. 4 At the end of the experimental part scanning electron microscopy and detailed elemental analyses were used for monitoring of the Ni-P particles nucleation and growth in the first 120 seconds of the coating process.
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Magnesium alloys
Březina, Matěj ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
The study is focused on corrosion and corrosion protection of magnesium and magnesium alloys. The theoretical part describes properties of magnesium and magnesium alloys. It shows their advantages as well as their disadvantages and discusses ideal use for these alloys. The theoretical part analyses basic corrosion characteristics and typical corrosion processes. It deals with types of corrosion protection and ways of its use. The experimental part was focused on metallographic analysis and corrosion behavior of magnesium alloy AZ91. Metallographic methods were used for preparing AZ91 to corrosion tests. The experimental part compared corrosion rate and degradation of pure AZ91 and AZ91 with conversion coating (phosphate-permanganate) in 3,5% sodium chloride solution in times: 1, 8 and 48 hours.
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Fluoride conversion coatings on magnesium materials
Staněk, Jan ; Wasserbauer, Jaromír (referee) ; Březina, Matěj (advisor)
This bachelor thesis deals with the topic of corrosion protection of magnesium materials by conversion coatings. The aim is to characterize and compare properties of fluoride conversion coatings formed on wrought magnesium sample and magnesium sample prepared by powder metallurgy. Basic knowledge of pure magnesium, magnesium alloys, powder metallurgy, corrosion, and protection against it are described in the theoretical part. Recent results of corrosion protection by fluoride conversion coatings on magnesium materials are summarised in the recherché part. The experimental part is focused on preparation of fluoride conversion coatings on each type of sample by immersion in Na[BF4] molten salt and by dipping in hydrofluoric acid. Surface morphology and composition of coatings were characterized by EDS analysis and corrosion protection was evaluated by potentiodynamic measurements.
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Evaluation of electrochemical characteristics of AZ61 magnesium alloy processed by squeeze casting
Pikner, Jan ; Hadzima, Branislav (referee) ; Fintová, Stanislava (advisor)
Bachelor thesis deals with the characterization of electrochemical corrosion properties of AZ61 magnesium alloy prepared by squeeze casting method. The theoretical part of the work focuses on properties of AZ61 alloy, influence of alloying elements on magnesium alloys and corrosion. The practical part of the work deals with electrochemical characteristics of AZ61 alloy with different surface condition in of 0.1 M NaCl solution. Corrosion potential (Ekor) and corrosion current density (ikor) were determined by potentiodynamic test. Polarisation resistance was determined by electrochemical impedance spectroscopy. Based on the measured results was discussed the influence of production, chemical composition, structure and surface treatment (grinding and polishing) on corrosion characteristics of the alloy.
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Processing of magnesium alloys using selective laser melting
Kaščák, Pavol ; Paloušek, David (referee) ; Suchý, Jan (advisor)
The processing of magnesium-based materials with Selective laser melting technology is due to its high reactivity in the initial stages of development. This bachelor thesis deals with the elucidation of impacts of individual process parameters in processing of magnesium alloys on the resulting material porosity. The aim is to develop initial experiments for the shift in the processing of magnesium alloys by additive technologies. The theoretical part contains an insight into the SLM technology and an overview of the current state of knowledge of processing of magnesium alloys by this technology. By the analysis of the theoretical part, the main volume test of this thesis has been designed. The selected material for this test was the biodegradable magnesium alloy WE43. According to the author's knowledge, no research has been published on this alloy so far. Based on the results of the experiment, the dependencies of the individual process parameters were made on the resulting relative density of the samples. At the end, the outputs were compared with the literature.
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Propsective surface treatments of magnesium alloys
Drábiková, Juliána ; Doležal, Pavel (referee) ; Zmrzlý, Martin (advisor)
The aim of this bachelor thesis is to summarize the methods of surface treatment of magnesium alloys and discussion of theireffectiveness of corrosion protection. In contrast to other metallic material used in technical practice, magnesium alloys have the lowest corrosion resistance, which can be increased by alloying or by use of surface treatments. The introduction part of the thesis deals with general knowledge about magnesium, its alloys AZ31, AZ91 and their corrosion processes. The recherché includes actual results of research about these alloys. Emphasizedare fluoride conversion coatings and composite coatings based on nickel, where their preparation is described and attention is focused on their properties in the sense of corrosion protection. Concluding the work, we give a critical assessment of the pros and cons of corrosion protective coatings on Mg alloys. Finally, there are suggested some convenient experiments to prove the repeatability of results published in the recherché literature.
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