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Preheating of the base plate during WAAM production of magnesium alloy AZ61
Zeman, Stanislav ; Hutař, Pavel (referee) ; Slavíček, Jakub (advisor)
The aim of this thesis was to design and construct a heated table, which was subsequently used to verify the effect of preheating on parts made by WAAM technology using AZ61 magnesium alloy as filler wire. The effect of preheating in the range of 50°C-350°C on the basic geometry of the single-track weld was successively investigated. It has been shown that the effect of preheating reduces hight and widens the geometry of the single-track weld, while deepening the penetration. Based on this knowledge, an ideal preheating temperature of 200 °C was determined for the production of thin-walled specimens. Preheating stabilized the width of the layers in the thin-walled specimen and significantly increased its quality. Furthermore, preheating was used to reduce residual stress. Strain measurements showed up to 50% residual stress reduction within the thin-walled specimen. Finally, a suitable temperature range of 200°C - 250°C was determined for WAAM fabrication of AZ61 magnesium alloy.
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Preparation and characterization of Ni-P coating on AZ91 cast magnesium alloy
Brescher, Roman ; Buchtík, Martin (referee) ; Wasserbauer, Jaromír (advisor)
This bachelor thesis deals with electroless deposition of nickel-phosphoric (Ni-P) coating on AZ91 magnesium alloy. At the beginning of the theoretical part, there is a summary of basic knowledge about magnesium alloys with focus on AZ91 alloy and the influence of alloying elements and impurities and its microstructure. The theoretical part continues with the discussion of the Ni-P coating, focusing on the composition of the bath, the influence and the effect of its individual components. Next, there is a comparison with galvanic nickeling. At the end of the theoretical part, the current research of the use of electroless deposition of Ni-P layer on AZ91 magnesium alloy is summarized. In the practical part, there is the preparation of the Ni-P coating on the AZ91 magnesium alloy, the observation the microstructure of the magnesium alloy and the Ni-P layer, and rate of deposition, the thickness, the microhardness and the composition of the coating was measured. The effect of its heat treatment was also observed. It has been found that it is possible to produce a high-quality Ni-P coating on an AZ91 magnesium alloy which has no visible defects or obvious undesirable interlayers, however the heat treatment of the coating causes its cracking. To determine the corrosion resistance, a potentiodynamic measurement was performed, resulting in the finding that the Ni-P coating without heat treatment was a suitable corrosion protection. However, after heat treatment, the corrosion resistance due to cracking of the surface deteriorated to a level of bare AZ91 alloy.
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Reactivity and controll of properties of metallic materials
Tkacz, Jakub ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
This thesis is focused on corrosion protection of magnesium alloys AZ 91. Very important is material corrosion in some environments and last but not least surface treatment as grinding, polishing and etching. Theoretical part of this thesis is about magnesium and magnesium alloy. It focuses on properties, in order to determine the best procedure for corrosion protection. It characterize material corrosion- for example corrosion in special environment (atmosphere, water, etc.) or elektrolyte corrosion. Big part of theoretical part is focused on electrochemistry, in particular kinetic aspects (Tafel diagrams, corrosion current, etc.) and potentiostatic testing, where are observed properties of material in relation to potential: corrosion potential Ecorr, brakedown potential Ebd and repassivation potential Erp. This work present preparing, utilization and positive or negative aspects of corrosion protection. Metallography is important too since metallographical preparation is crucial for the research on the material. Described metallography procedures are mounting, grinding, polishing, etching and interpretation. Experimental part of this thesis is in particular about corrosion properties of magnesium alloy AZ 91. It focuses on calculation of corrosion rate in defferent environments. Principle is mass defekt of the alloy. The environments are: destilled water, hot service water and 3% NaCl solution (like sea water). Last but not least are important. procedure manipulation with materials. Very important are choice and composition of solutions, etching time, choice of polishing cloth, lubricant solution and good pressure. Beacuse of this aspects can be show corrosion action of environments on magnesium alloy AZ 91 by photographies.
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Conversion coatings and their characterisation
Březina, Matěj ; Doležal, Pavel (referee) ; Zmrzlý, Martin (advisor)
Aim of this study is to improve corrosion resistance of magnesium alloy AZ91 by conversion coatings. Influence of alloy microstructure on conversion coating growth and corrosion resistance was evaluated. Properties of pure magnesium and magnesium alloy AZ91 as well as the influence of alloying elements on properties of this alloy are described in theoretical part. Recent results of corrosion protection by conversion coatings on AZ type magnesium alloys are summarised in recherché part. Practical part focuses on preparation of hexavalent chromium based conversion coating and phosphate-permanganate based conversion coating on as cast AZ91 magnesium alloy, these coatings were subsequently applied on annealed AZ91 magnesium alloy. Corrosion protection of the coatings prepared on as cast and annealed alloy was evaluated by potentiodynamic measurements and testing in neutral salt spray. Furthermore the influence of plasma activation on phosphate-permanganate coating surface was studied.
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Influence of surfactants in electroless nickel bath on properties of Ni-P coatings on AZ91 magnesium alloy
Buday, Patrik ; Wasserbauer, Jaromír (referee) ; Buchtík, Martin (advisor)
This bachelor thesis deals with the effect of surfactants on mechanical properties and structure of Ni-P coatings on AZ91 magnesium alloy. The theoretical part of the thesis includes summary of basic knowledge about magnesium alloys, surfactants and electroless deposition of Ni-P coatings, including a detailed description of Ni-P reduction on substrate. The theoretical part is concluded by current research in the field of Ni-P coatings. In the experimental part, morphology of Ni-P coatings was observed by electron microscopy (SEM). Using a light microscope (LM), the effect of surfactants on the deposition rate was observed. By means of energy dispersion analysis, the average phosphorus content of Ni-P coatings was determined. The hardness as a mechanical property of these coatings was determined using a micro hardener.
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The History of Non-Ferrous Alloys in Aircraft Industry
Dušek, Přemysl ; Gejdoš, Pavel (referee) ; Němec, Karel (advisor)
Main part bachelor work be concerned common description magnesium alloys,compare with aluminium alloys,benefits or disadvantages magnesium alloy,describe groups of magnesium alloys after alloying component,technological properties and heat treatment.Next part my bachelor work includes application magnesium alloys in aircraft constructions from second worl war in Germany to present day.
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Influence of fabrication and alloying on magnesium alloys
Jakl, Tomáš ; Remešová, Michaela (referee) ; Horynová, Miroslava (advisor)
This bachelor thesis compares mechanical properties of magnesium alloys in dependence on their composition and fabrication. The first part deals with a pure magnesium and its properties. The second part contains information about alloying elements and an overview of the fabrication methods. The third part consists of different magnesium alloys. The thesis contains photographs of microstructures, a review of mechanical properties and their comparison.
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