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Local tests of mechanical properties of materials
Wasserbauer, Jaromír ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
This thesis deals with measurement of hardness and microhardness in relation to structure of homogeneous and heterogeneous materials. In the introduction basic theoretical background is commented, i.e. definitions, terminology, principles of measuring techniques for estimation of hardness, microhardness, tensile strength, compressive strength and bending strength. Follows a brief review of present research results focused on use of described principles in materials engineering. Then the experimental equipment and sample preparation is described. The crucial part of the thesis is summary of achieved results of original measurement and discussion of their relations to each other. Finally, the groundbreaking estimation is described, showing the correlation of chemical composition gradient and mechanical properties in interfacial zone of geopolymeric material.
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Complete characterization and comparison of lacquer / Ni-P / AZ91 and lacquer / AZ91 systems
Šomanová, Pavlína ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
The aim of this bachelor thesis was to compare the influence of Ni-P coating and varnish on the corrosion properties and chemical – physical properties (adhesion) of the magnesium alloy AZ91. The theoretical part contains the information about the alloy AZ91 itself and its microstructure, following by discussion about Ni-P coating, its properties, the process of the electroless deposition and composition it the nickel bath. Next chapter focuses on information about varnishes, its function and the process of its application on the surface of the substrate. Theoretical part closes with the summary of current research in the field of Ni-P coatings applied on magnesium alloys. The experimental part focuses on analysis of the microstructure of AZ91 alloy. The microstructure of the Ni-P coating and of the system Mg alloy/Ni-P coating/varnish was 4 examined by scanning electron microscope (SEM) and inverted microscope. During the next phase was thickness and hardness measured and composition measured by EDS analysis. The factor of the heat treatment of the samples and its impact on the final microstructure, hardness and corrosion resistance was taken in account. Finally, several samples were modified with the layer of the varnish and its thickness and the influence on the corrosion resistance ware measured. Samples were tested with electromechanical impedance spectroscopy (EIS), the corossion resistance were tested by neutral salt spray (NSS) and adhesive test was performed. The results showed, that Ni-P coating and the layer of varnish had positive impact on the corrosion resistance and the hardness of AZ91. The corrosion resistance of the samples modified with heat treatment was much lower, because of the contracting, which causes creation of the cracks. Also, the layer of varnish had positive effect on anticorrosion properties of tested AZ91 alloy.
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Multi-element Systems of Biomaterials Based on Magnesium and Zinc
Hasoňová, Michaela ; Nový, František (referee) ; Vojtěch, Dalibor (referee) ; Doležal, Pavel (advisor)
Dissertation thesis deals with basic research in the field of materials from pure Zn powders and Mg, Zn, and Ca binary mixtures prepared by powder metallurgy. General powder metallurgy principles and methods, a brief description of Mg, Zn, and Ca structure and properties, and the latest research in the field of bulk materials preparation from these elements via powder metallurgy are summarized in the theoretical part of the thesis. The experimental part focuses on the preparation of materials from finer and coarser Zn powder particles by hot pressing at 300 and 400 °C using the pressure of 100, 200, 300, 400, and 500 MPa. Binary mixtures based on Mg with the addition of Zn or Ca were prepared by hot pressing in the solid-state (300 °C) and hot pressing in the semi-solid state (400 °C, 450 °C in the case of Mg-Ca system) using the pressure of 500 MPa. Binary mixtures based on Zn with the addition of Mg or Ca were prepared by hot pressing in the semi-solid state (400 °C) using the pressure of 500 MPa. The prepared materials were evaluated in terms of microstructure, elemental and phase composition, microhardness, flexural strength, and fractography. The results showed that in the case of processed from pure Zn powders, a better combination of the flexural strength and displacement was achieved in the case of the finer Zn powder, namely in the material prepared at a temperature of 400 °C and a pressure of 500 MPa. In the case of mixtures, the best connection between the powder particles was achieved in the case of a material based on finer Zn powder with 0.5 wt.% of Mg, which had a significant effect on the achieved values of flexural strength and displacement. The amount of minor powder in the mixture had a significant effect on the prepared material structure and phase composition, while the processing conditions influenced the reached strength characteristics and fracture mechanism.
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Analysis of Inconel 625 weld layer produced by MIG-CMT
Chrást, Daniel ; Slováček, Marek (referee) ; Kubíček, Jaroslav (advisor)
Návary z materiálu Inconel 625 na základní materiál 16Mo3 slouží v energetickém průmyslu u spaloven odpadu pro zvýšení životnosti membránových stěn. Návarové housenky jsou vytvořeny pomocí metody MIG-CMT. Byly provedeny analýzy makrostruktury a mikrostruktury za použití SEM mikroskopu Apreo 2, dále byla provedena analýza chemické složení návarové housenky za použití OES spektrometru ISpark. Nakonec byly provedeny analýzy vybraných mechanických vlastností, konkrétně mikrotvrdost a tažnost.
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Optimizing the Properties of the Coatings prepared by the Cold Spray Method using Heat Treatment
Bartošík, Vojtěch ; Šmíd, Miroslav (referee) ; Hutařová, Simona (advisor)
This bachelor's thesis deals with the choice of heat treatment parameters of the metal coating of austenitic unstabilized stainless steel AISI 304L applied by the Cold spray method. With the help of suitable heat treatment, it is possible to adjust the mechanical properties, reduce the porosity and, last but not least, also remove high residual stresses in the material. The theoretical part of the work is devoted to literature research on the topic of Cold spray technology, corrosion and corrosion-resistant steels. The experimental part describes the procedures for measuring samples that have undergone heat treatment. This took place in the temperature range of 500 to 1100 °C, always with an hour's holding time at the temperature, followed by cooling in air. In addition to these samples, the material was also examined in its initial state. Porosity, microhardness and also magnetism were determined. To analyze the structure, photographs were taken on a light and electron scanning microscope. Based on the results, heat treatment with an hourly hold at 700 °C seems to be a good choice, where a significant decrease in porosity, partial recovery of the structure while maintaining high microhardness and also grain fineness was observed.
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Phase transformation in magnesium MgZnAl-based alloys
Kodetová, Veronika ; Vlach, Martin (advisor) ; Mathis, Kristián (referee)
In the present work, there was analyzed thermal evolution of the phase transformation in the MgZnAl and MgZnAlCa alloys with different concentration of the Zn and Ca. The grains were occupied by the phase with quasicrystaline icosaedral structure in the as-cast alloys and after isochronal annealing up to 240 řC. The thermal measurements revealed two exothermic effects in the MgZnAl alloy and three exothermic effects in the MgZnAlCa alloy during linear heat treatment in the temperature range of 100 - 250 řC. In agreement to the thermal response, two and three stages of electrical resistivity decrease were observed in the same temperature range. The lower thermal changes, absolute resistivity changes and microhardness were observed in the alloy with Ca-addition and lower concentration of Zn.
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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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Phase transformation in magnesium MgZnAl-based alloys
Kodetová, Veronika ; Vlach, Martin (advisor)
In the present work, there was analyzed thermal evolution of the phase transformation in the MgZnAl and MgZnAlCa alloys with different concentration of the Zn and Ca. The grains were occupied by the phase with quasicrystaline icosaedral structure in the as-cast alloys and after isochronal annealing up to 240 řC. The thermal measurements revealed two exothermic effects in the MgZnAl alloy and three exothermic effects in the MgZnAlCa alloy during linear heat treatment in the temperature range of 100 - 250 řC. In agreement to the thermal response, two and three stages of electrical resistivity decrease were observed in the same temperature range. The lower thermal changes, absolute resistivity changes and microhardness were observed in the alloy with Ca-addition and lower concentration of Zn.
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