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Malonate and succinate as potential corrosion inhibitors of AZ31 magnesium alloy in 0.9% NaCl
Tkáčová, Karolína ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The aim of this work was to evaluate the inhibitory effects of malonic acid, succinic acid and their mixture in a 0,15M NaCl solution at pH 7 on AZ31 magnesium alloy. The theoretical part focuses on magnesium, its alloys and alloying elements. It also discusses magnesium corrosion in aqueous environments and the influence of microstructure on corrosion. The final section is dedicated to corrosion inhibitors and small aliphatic acids. The practical part of this work involves potentiodynamic measurements, immersion tests, and subsequent analysis of alloy surfaces. The following concentrations of acids were chosen for studying inhibitory properties: 0.025M, 0.05M, 0.075M, and 0.1M, as well as various mixtures of both acids. Suppression of corrosion was observed in immersion tests for both acids individually and in their mixture. The best inhibitory results in both potentiodynamic polarization (PDP) analysis and immersion tests were achieved with a mixture of 0.025M malonic acid solution and 0.075M succinic acid solution.
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Development of WAAM process parameters for thin-walled components made of magnesium alloy AZ61
Šváb, Čeněk ; Němeček, Stanislav (referee) ; Slavíček, Jakub (advisor)
The thesis deals with the development of WAAM (Wire Arc Additive Manufacturing) process parameters for thin-walled parts made of magnesium alloy AZ61. The aim of the thesis is to find suitable process parameters and describe their influences on the welding process. To achieve this goal, these parameters were experimentally tested. It was found that the parameter of boost phase current and the duration of its application have the highest influence on the weld geometry. The stability of the welding process was then influenced by the electrode feed rate during the boost and burn phases. Based on these results, a final set of parameters was created, which successfully welded a thin-walled part composed of 50 layers and reaching a height of 130 mm.
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Mechanical properties of magnesium alloy AZ91E prepared by ECAP method
Darida, Jiří ; Válka, Libor (referee) ; Pantělejev, Libor (advisor)
This thesis deals with mechanical and fatigue properties of magnesium alloy AZ91 processed by EX-ECAP method. This method involves the application of extrusion followed by equal-channel angular pressing. To obtain basic mechanical characteristics, the tensile test were carried out at room and elevated temperatures. Further the fatigue tests were performed and obtained data were used to compile S-N curve. The work also includes metallographics analysis of microstructure and fractographic analysis of fracture surfaces of tensile and fatigue test specimens.
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Ni-P based coatings preparation on wrought magnesium alloys
Buchtík, Martin ; Fintová, Stanislava (referee) ; Wasserbauer, Jaromír (advisor)
The aim of this diploma thesis was summary of all steps and knowledge necessary to deposition of quality Ni-P coatings deposited on wrought magnesium alloys AZ31 and AZ61. There is the treatise about wrought magnesium alloys AZ31 and AZ61. Thesis includes its phase composition in the theoretical part. There are given its possible processing methods too. Next, there is desribed the mechanism of deposition of Ni-P coatings, components required to electroless deposition and factors affecting the quality and properties of these coatings. The theoretical part is ended by serie of reviews. Authors of these reviews deal with pretreatment of substrates, preparation, characterization and measuring of mechanical, structure and corrosion properties of deposited coatings. The optimalization of pretreatment, parametres and composition of nickel bath suitable for magnesium alloys is described in experimental part. The microstructure, present interlayer between substrate and Ni-P coating and chemical composition of deposited coatings was observed and measured by optical and electron microscopy. The mechanical characterization of Ni-P coatings was performed by microhardness tester.
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Preparation and Characterization of Advanced Thermally-sprayed Coatings on Magnesium Alloys
Buchtík, Martin ; Hadzima, Branislav (referee) ; Fintová, Stanislava (referee) ; Ptáček, Petr (advisor)
The proposed dissertation thesis deals with the characterization of HVOF and APS-thermally sprayed coatings prepared on the AZ31 and AZ91 magnesium substrates. The theoretical part of the thesis describes in-detail Mg substrates used in the experimental part of the thesis. There are also characterized materials and coatings based on NiCrAlY and FeCrNiMoSiC metals, WC-CoCr cermets, and YSZ ceramic materials. At the end of the theoretical part, the literary research summarizing the characterization and analysis performed on thermally sprayed coatings on Mg alloys. Based on the theoretical knowledge, the characterization of Mg substrates and deposited coatings was performed in terms of the surface morphology, microstructure, and the chemical composition using the light microscopy (LM) and scanning electron microscopy with energy-dispersive spectroscopy (SEM+EDS). The phase composition of the coatings was analyzed using the X-ray diffraction (XRD). The diffractions corresponding to the sprayed coatings were compared with the feedstock powders, i.e. materials used for the spraying of the coatings. The characterization of the prepared coatings in terms of the mechanical and tribological properties was performed. The hardness and microhardness of the coatings as well as the coefficient of friction, and the wear rate were measured. The last chapter of the experimental part deals with the evaluation of the electrochemical corrosion properties by the potentiodynamic measurements in a 3.5% NaCl solution. In the case of exposed samples, the evaluation of the surface and coating/substrate interface was performed using LM and SEM with EDS. The mechanism of the corrosion attack and degradation was determined from the acquired knowledge and base on the results of the short-term measurements. Based on the measured results, it can be stated that the deposited coatings were successfully applied on the surface of both Mg alloys. All the coatings increase the surface hardness of the Mg alloys and significantly improve their tribological properties. However, except for FeCrNiMoSiC coatings, the corrosion properties of Mg alloys deteriorate due to the fact that the corrosion environment can pass through the coating to the less noble Mg substrate and the corrosion microcells are created.
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Study of the microstructure of deposited Ni-P coatings with different phosphorus contents
Najser, Tomáš ; Kosár, Petr (referee) ; Wasserbauer, Jaromír (advisor)
The aim of this bachelor thesis was the preparation and characterization of Ni-P coatings with different phosphorus contents on the substrate of AZ91 magnesium alloy. The theoretical part deals with magnesium alloys and specifies the utilized substrate AZ91. It also focuses on Ni-P coatings, their microstructure and their properties. However, there are also described factors affecting the rate of deposition and the resulting behavior of these coatings. Last but not least, the theoretical part summarizes the basic principles of laboratory methods used in the experimental part for observation and characterization of samples. Conclusion of the theoretical part consists of several background researches where the authors deal with similar problems and factors influencing the resulting behavior of Ni-P coatings. The experimental part is focused on the deposition of each Ni-P coatings on the AZ91 alloy and their characterization. The study of deposited Ni-P layers was focused on the determination of their microstructural texture by XRD method, mechanical properties and elemental composition depending on phosphorus content.
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Galvanic plating of magnesium alloy with Ni-P bond coat
Zahálka, Martin ; Kosár, Petr (referee) ; Wasserbauer, Jaromír (advisor)
Cílem této diplomové práce jse najít nejnižší možnou tloušťku nikl-fosforového povlaku, který může být galvanicky pokoven mědí bez defektů na horčíkové slitině, nikl-fosforového nebo měděného povlaku. V teoretické části jsou shrnuty poznatky o hořčíkových slitinách a jejich korozi. Navíc se teoreticá část zaměřuje na popis procesu bezproudého niklování a elektrochemického pokovování mědí a jejich porovnání. Na konci teoretické části je shrnut současný výzkum o elektrochemickém pokovování hořčíkových slitin. V experimentální části byl popsán proces přípravy povlaků Ni-P a Cu na horčíkové slitině AZ91. Na jedné vrstvě a dvojité vrstvě Ni-P povlaku byla provedena elektrodepozice mědi. Navíc byl diskutován vliv předůpravy před samotnou elektrodepozicí mědi. Za účelem zjištění korozních vlastností vzorků byl vykonán potenciodynamický test. Následně byly připraveny metalografické výbrusy jednotlivých vzorků a pomocí světelného a rastrovacího elektronového mikroskopu byla provedena charakterizace. Na konec bylo zjištěno prvkové složení jednotlivých povlaků pomocí EDX analýzy.
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Evaluation of corrosion properties of biodegradable ZE41 magnesium alloy
Honč, Jiří ; Minda, Jozef (referee) ; Tkacz, Jakub (advisor)
This thesis deals with evaluation of corrosion properties of biodegradable magnesium alloy ZE41. Corrosion characteristics of ZE41 wrought magnesium alloy specimens with polished and grinded surface were examined by electrochemical methods. 0,1M NaCl solution was used as corrosive environment. Short-term tests were performed using linear polarization method, by which the corrosion potential, corrosion current density and corrosion rate was determined. Long-term evolution of corrosion behavior in terms of polarization resistance was studied by electrochemical impedance spectroscopy (EIS) during 168 hours. Also, the corrosion products were characterized by scanning electron microscope (SEM) with energy-dispersive spectroscopy (EDS). Based on the results, the influence of phase composition and surface treatment on corrosion characteristics was discussed.
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Fatigue Behaviour of AZ31 and AZ61 Magnesium Alloys
Gejdoš, Pavel ; Lukáč, Pavel (referee) ; Kohout, Jan (referee) ; Podrábský, Tomáš (advisor)
This doctoral thesis deals with the fatigue behaviour of AZ31 and AZ61 magnesium alloy casted by advanced methods of casting squeeze casting. Based on the regression functions and measured fatigue data were determined fatigue characteristics of these alloys. The work also extends into the area of fatigue cracks in the AZ31 alloy. Were measured fatigue crack propagation rate on modified cylindrical specimens. The paper also outlines the possibilities for describing the fatigue behaviour of AZ61 alloy in extremely low-cycle fatigue.
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Evaluation of Corrosion on Selected Magnesium Alloys
Pořický, Vladislav ; Tulka,, Jaromír (referee) ; Pacal, Bohumil (advisor)
This master´s thesis is focused on classification of corrosion resistivity magnesium alloy type AZ91 in environment of salt vapour testing in corrosion chambers. For tests were used samples of magnesium alloy manufactured by three different methods of casting: cast-iron mold, die vacuum casting, die casting without vacuum and method of die casting with additional pressure (squeeze casting). In this work was accomplished metallographic evaluation of corrosion attack and detailed analysis of corrosion products. Conclusions of exposits tests are assembled of analysis of influence of corrosion environment on structure of alloy. On the basis of these conclusions of corrosion tests were evaluated influences of corrosion speed [mm/year] on time [hours] for individual states of magnesium alloy.
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