TiAlN and TiAlN-based coatings that are used of relevance as protection of cutting tool inserts used in metal machining have been studied. All coatings were deposited by reactive cathodic arc evaporation using industrial scale deposition systems. The metal content of the coatings was varied by using different combinations of compound cathodes. The as-deposited coatings were temperature annealed at ambient pressure and in some cases also at high pressure. The resulting microstructure was first evaluated through a combination of x-ray diffraction and transmission electron microscopy. In addition, mechanical properties such as hardness by nanoindentation were also reported. TiAlN coatings with two different compositions were deposited on polycrystalline boron nitride substrates and then high pressure high temperature treated in a BELT press at constant 5.35 GPa and at 1050 and 1300 °C for different times. For high pressure high temperature treated TiAlN it has been shown that the decomposition is slower at higher pressure compared to ambeint pressure and that no chemical interaction takes place between TiAlN and polycrystalline cubic boron nitride during the experiments. It is concluded that this film has the potential to protect a polycrystalline cubic boron nitride substrate during metal machining due to a high chemical integrity. TiZrAlN coatings with different predicted driving forces for spinodal decomposition were furthermore annealed at different temperatures. For this material system it has been shown that for Zr-poor compositions the tendency for phase separation between ZrN and AlN is strong at elevated temperatures and that after spinodal decomposition stable TiZrN is formed.

While using iron castings behind temperature of 500 C namely at cyclic heat straining degradation of structure and breaching iron castings. For this purpose introduce cast iron with content of Si and Mo. Focusing on improvement of SiMo51 for increased high-temmperature corrosion-and fatigue life in exhaust-gas temperatures up to 800 C. Thesis set up chemical microheterogeneity, properties, high temperature corosion and microhardness

This thesis is focused on processing of pure magnesium by high pressure torsion method (HPT). This process belongs to the group of intensive plastic deformation methods (SPD). SPD methods are in the centre of scientific interest for several decades. Theoretical part of this thesis puts an effort to summarize basic knowledge and principles of SPD methods with extra focus on method HPT. As theoretical part continues magnesium as technical material is presented. Influence of SPD on use and properties of pure magnesium is then presented. This trend is further developed in effort to describe the effect of individual HPT process variables on the properties of pure magnesium and its alloys. Focus of practical part of this thesis is in influence of number of revolutions. Samples were processed at 1/8, 1/4, 1/2, 1, 4 and 8 turns at room temperature. Speed of process was 1rpm and applied pressure was 6 GPa. The structure of commercially pure magnesium prepared by casting and moulding were observed with focus on differences caused by input material. The structure was observed by both light microscopy and back scattered electron diffraction (EBSD), focusing on structure development, grain size and grain orientation. Compared to other works on similar topic, the emphasis here is on observing the microhardness on the vertical edge of the sample. The hardness shows a steep increase right after 1/8 of a turn. With increasing number of turns gradual homogenization of microhardness is presented accompanied by slight decrease in microhardness. No trend in microhardness relative to the distance from anvil has occurred. Structure observed with EBSD shows a bimodal character with larger grains oriented in the same direction. The three-point bending test didn’t end up as expected, and the approach to evaluation of magnesium-based HPT needs to be re-evaluated for future work. A three-point bending test was designed for the initial assessment of the basic mechanical properties of the material.

This thesis deals with study of surface layers of low-carbon steels formed by chemical-heat treatment. The first three chapters consist of theoretical part of the thesis, there are explained basic physical principles of these technologies and described individual types, the third chapter deals with the application of chemical-heat treated low-carbon steels in mechanical engineering. The experimental part of thesis deals with analysis of surface layers of two low-carbon steels formed using plasma nitrocarburizing and gas nitrocarburizing. The properties of these layers are evaluated based on the results of mechanical tests (hardness tests) and observation of microstructure. The thesis is completed by discussion, where the achieved results are evaluated.

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.

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.

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.

Indiana University-Purdue University Indianapolis (IUPUI) / Objective: This study aimed to evaluate surface microhardness changes in early, incipient, non-cavitated white-spot, enamel caries lesions treated with silver diamine fluoride (SDF) longitudinally. The utilization of silver nitrate and potassium fluoride test groups served as additional controls to assist in evaluating if the remineralization effects were due to the silver or fluoride component in SDF. Hypotheses: 1. SDF treatment will result in increased surface microhardness of early, incipient, non-cavitated white-spot, enamel caries lesions compared to all other tested interventions. 2. Specimen storage for 2-weeks in artificial saliva will result in greater surface rehardening in lesions treated with SDF compared to other tested interventions. Design: This laboratory study had 5 intervention groups (SDF, silver nitrate (AgNO3), potassium fluoride (KF), 5.0-percent sodium fluoride varnish (FV), deionized water (DI)) × 2-time intervals after intervention (immediate & delayed pH-cycling), resulting in 10 groups (n = 18). Early, incipient, non-cavitated white-spot, enamel caries lesions were created in bovine enamel and extent of demineralization was determined using Vickers surface microhardness (VHNlesion). Intervention treatments were applied. Half the specimens from each group underwent immediate 5-day pH-cycling and half were stored in an incubator with artificial saliva for two weeks before undergoing 5-day pH-cycling. After pH-cycling, lesion hardness was evaluated using VHNpost. Specimens were then exposed to a second demineralization challenge and lesion softening was evaluated using VHNsecdem. Surface rehardening was calculated: ΔVHN =VHNpost - VHNlesion. Surface softening was calculated: ΔVHNsecdem =VHNsecdem – VHNpost. Data was analyzed using two-way ANOVA. Results: Immediately cycled, SDF had significantly (p < .0001) greater remineralization than DI, AgNO3, and FV. All delayed cycling groups had significantly (p < .0001) greater remineralization than FV. Significantly greater remineralization was noted in delayed AgNO3 (p < .0001), DI (p = .0003), and FV (p = .0006) compared to immediately cycled. After the second demineralization challenge, FV had significantly less surface softening than AgNO3 (p = 0.0002), DI (p = 0.0003), KF (p = 0.0225), and SDF (p = 0.0388) intervention groups. No significant difference was found between the pH-cycle timings. Conclusion: Based on our findings, FV maybe better suitable than SDF to treat early, incipient, non-cavitated white-spot, enamel caries lesions. Longitudinally, SDF exhibited greater remineralization than both FV and DI groups, though not statistically significant. However, upon a second demineralization challenge, FV significantly outperformed SDF in preventing surface softening. / 2021-09-30

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Объектом исследования являются медь и малолегированные бронзы, подвергнутые интенсивной пластической деформации. Целью работы было определение текущего состояния научных исследований по использованию меди и малолегированных бронз. А также предложить состав и исследовать структуру и свойства бронзы выбранного состава после интенсивной пластической деформации методом динамического канально-углового прессования. В процессе работы проводился анализ литературных источников. В результате исследования было установлено текущее состояние по проблематике работы и определен вектор исследований. Методами оптической металлографии, дюрометрического анализа, просвечивающей электронной микроскопии и сканирующей электронной микроскопии с применением дисперсионно-энергетического анализа и анализа на основе обратного рассеяния электронов было проведено исследование сплава Cu-0,8 вес.% Hf. При различных обработках методом динамического канально-углового прессования. Эксперимент включал различное состояние бронзы перед деформированием. Также было проведено исследование термической стабильности полученных методом динамического канально-углового прессования образцов. Было установлено, что гафниевая бронза после прессования обладает высокими механическими характеристиками и ультрамелкодисперсной структурой. При этом полученная структура стабильна при комнатной температуре и при последующем отжиге вплоть до 400 °С. Что позволяет рекомендовать данный материал как основу для широкого спектра электротехнических изделий. / The object of research is copper and low-alloy bronzes after severe plastic deformation. The purpose of this work was to review scientific research on the use of copper and low-alloy bronzes. As well as the development of the composition and study of the structure and properties of bronze after severe plastic deformation by the method of dynamic channel-angular pressing had been carried out. Literature analysis was carried out. Methods of optical metallography, durometric analysis, transmission electron microscopy and scanning electron microscopy using energy dispersion analysis and analysis based on electron backscattering had been used to study the Cu-0.8 wt.% Hf alloy. Various processings had been carried out by the method of dynamic canal-angular pressing. The state of the bronze before deformation was variouse. We also studied the thermal stability of samples obtained by the method of dynamic channel-angular pressing. It was found that hafnium bronze after pressing has high mechanical characteristics and an ultrafine structure. In this case, the resulting structure is stable at room temperature and upon subsequent annealing up to 400 °C. That allows us to recommend this material as a basis for a wide range of electrical products.