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Microstructure and Properties of Spark Plasma Sintered Al-Zn-Mg-Cu Alloy.
Zyka, J. ; Málek, J. ; Pala, Zdeněk ; Andršová, I. ; Veselý, J.
High entropy alloys are a new material class with promising structural and mechanical properties in wide range of applications. In principle they consist of five or more elements in equimolar concentrations resulting basically in single phase microstructure. TaNbHfZrTi alloy was developed by Senkov for high temperature applications.\nSince all of these elements are biocompatible the TaNbHfZrTi alloy can be investigated as a prospective bio implant material. The alloy was prepared by vacuum arc melting, no annealing treatment was applied. Tensile test and hardness test at room temperature were performed with very good results: yield strength 1155 MPa, rupture strength 1212 MPa, Vickers hardness 359 HV30. Microstructure and fracture morphology was also investigated.
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První experimenty s přípravou suspenzního nástřiku Al2O3 pomocí hybridního plazmového hořáku
Tesař, Tomáš ; Mušálek, Radek ; Medřický, Jan ; Kotlan, Jiří ; Pala, Zdeněk
Hybridní vodou stabilizovaný hořák WSP-H představuje zajímavou alternativu k běžným hořákům pro žárové stříkání, neboť poskytuje jedinečnou kombinaci rychlosti plazmatu a entalpie dostupné pro zpracování materiálu. V této práci je studován vliv depozičních parametrů na charakteristiky nástřiku. Jako modelový materiál byl použit nanometrický Al2O3 dispergovaný v etanolu. Nástřik byl zkoumán pomocí skenovací elektronové mikroskopie a rentgenové difrakce. Výsledky prokázaly závislost charakteru mikrostruktury a fázového složení na podávací vzdálenosti a podávaném množství suspenze. Výsledky jsou zajímavé pro další optimalizaci depozičního procesu
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Composites of titanium carbide with scandium matrix
Brožek, Vlastimil ; Pala, Zdeněk ; Vilémová, Monika ; Kubatík, Tomáš František ; Mušálek, Radek ; Nevrlá, Barbara ; Mastný, L.
First reference about existence of ultrahard composite in the TiC-ScCx system was made by G.V. Samsonov in the year 1962. Further research performed on ICT Prague and University of Vienna proved a discrepancy in the structure and stoichiometry of scandium carbide. Analogously to cubic carbides and nitrides of 3rd period metals, Scandium was also expected to have extreme hardness, high chemical stability and to enable solid solution formation (Vegard rule) with controlled regulation of physical parameters. Higher hardness of the cubic carbides is related to the decrease of lattice parameter, thus is was expected that smaller atomic radius of Sc in TixSc1-xC solid solution will lead to increase in hardness. However it was discovered that scandium carbide differs chemically as well as structurally, e.g. Sc15C19 is hydrolyzed and the product of the reaction is hydrogen, allylen and other hydrocarbons. Due to high price of Sc compounds, CVD and PVD layers of TiAlN or TiScAlN on sintered
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Preparation of multiphase materials with spark plasma sintering
Mušálek, Radek ; Dlabáček, Zdeněk ; Vilémová, Monika ; Pala, Zdeněk ; Matějíček, Jiří ; Chráska, Tomáš
Spark plasma sintering (SPS), also called Field Assisted Sintering Technique (FAST), represents a novel method of preparation of sintered materials from powders. The main advantage of the SPS method is a high achievable heat rate (>200 °C/min) and high sintering temperatures (up to 2200 °C in our laboratory). Combination of high heating rate, rather high pressures (up to 80 MPa) and electric field fluctuations leads to an effective sintering and significant reduction of sintering time for both coarse-grained and nanocrystalline powders. Composite materials may be easily obtained by mixing or layering of different powders. The paper will introduce several examples of multiphase materials sintered by SPS at our institute and the establishment of procedures for routine testing of sub-sized specimens.
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Tungsten-Steel Composites and FGMs Produced by Hot Pressing
Matějíček, Jiří ; Boldyryeva, Hanna ; Brožek, Vlastimil ; Čižmárová, E. ; Pala, Zdeněk
Tungsten-steel composites and FGMs are being developed for potential application in plasma facing components of fusion devices. In this study, uniform composites and graded layers produced from tungsten and steel powders by hot pressing were investigated. Formation of dense composites with uniform distribution and good bonding of the phases was observed. A thin layer of intermetallic phase Fe7W6 formed at the interfaces. Thermal and mechanical properties of the composites in the as-produced and annealed state were characterized.
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