Národní úložiště šedé literatury Nalezeno 2 záznamů.  Hledání trvalo 0.00 vteřin. 
Metal Matrix Composites Prepared by Powder Metallurgy Route
Moravčíková de Almeida Gouvea, Larissa ; Novák, Pavel (oponent) ; Hadraba, Hynek (oponent) ; Dlouhý, Ivo (vedoucí práce)
The development of new materials for applications in extreme environments is currently of a great importance in modern engineering technologies. Hence, the industries' requirement for enhanced structural performance of materials is constantly increasing. In the light of that, this study aims to evaluate promising compositions of high-entropy alloys for critical applications produced by powder metallurgy through a combination of mechanical alloying and solid state sintering. For comparative purposes, the selected compositions were produced by melting routes in liquid state as well, such as vacuum induction melting and subsequent casting or vacuum arc-melting. The powder metallurgy route enables a consequential development of metal matrix composites (MMC) via the manufacturing of oxide dispersed strengthened HEAs. This is possible due to inherent in-situ reactions during the process. In case of melting route fabrication, metallic materials with great differences in structures and related properties are manufactured, compared to those produced by powder routes. The produced MMCs and their melted counterparts are thoroughly studied. A comprehensive evaluation of the influence of the different processing methods, especially on the materials’ microstructural features and their mechanical properties is undertaken, including the effect of heat treatments on the phase transformations and stability of the materials.
Effect of heat treatments on the microstructure and hardness of high-entropy alloy
Jesenská, Mária Ľudmila ; Adam, Ondřej (oponent) ; Moravčíková de Almeida Gouvea, Larissa (vedoucí práce)
In this work, a non-equiatomic Al0.2Co1.5CrFeNi1.5Ti high-entropy alloy was produced through the vacuum induction melting process. The as-cast alloy was analyzed, then heat treated at 1000 °C for 5h, and subsequent heat treatment at 750 °C for an additional 5h took place, in order to investigate the effect of heat treatment temperature and time on the phase composition, microstructure, and mechanical properties of the alloy in all states. A pseudo binary phase diagram (CALPHAD) was performed to evaluate the possible phases present in the alloy. The alloy‘s microstructures were characterized and analyzed chemically by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Microhardness and nanoindentation testing was performed to evaluate the hardness of the material.

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