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Zn and Mg based bulk materials for biomedical applications
Ryšťák, Jaroslav ; Fintová, Stanislava (referee) ; Doležal, Pavel (advisor)
Topic of the diploma thesis is Zn-Mg bulk material preparation by powder mixtures sintering at hot pressing. Structure, porosity and physically mechanical properties of prepared bulk materials were evaluated. Obtained results and their interpretation were served as feedback for following optimization of individual processing parameters of bulk materials preparation. Solution of diploma thesis is focused on study and control of processes during bulk material preparation and processes description from physical-chemical point of view with respect to structure creation and final material properties.
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Morphology and hardness of particles of titanium powder prepared by cryogenic milling
Ibragimov, Ilya ; Stráský, Josef (advisor) ; Janeček, Miloš (referee)
The effect of cryogenic milling on morphology and microhardness of titanium powder was investigated. Initial powder of commercially pure titanium was subjected to cryogenic milling in liquid argon (LAr) using two different milling speeds. Prepared powders were subsequently cleaned by ethanol. The cleaning procedure was done in two ways: in the air and in the inert atmosphere in the glovebox. Particle size and morphology were investigated my scanning electron microscopy and subsequent automated image analysis. Microhardness of powder particles was determined by Vickers hardness measurement using small loads. The milling did not cause significant powder refiniment, while the shape of powder particles changes substantially. Milling speed affected particle shape and powder contamination. Application of stearic acid as the processing control agent prevented cold-welding of powder particles, but contaminated the powder by oxygen and hydrogen. Stearic acid could be successfully removed by cleaning in ethanol. The using of glovebox for cleaning did not have significant effect on the resultiing contamination.
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In-situ Synthesised Intermetallic Compounds in Powder Materials
Hanusová, Petra ; Novák, Pavel (referee) ; Skotnicová, Kateřina (referee) ; Dlouhý, Ivo (advisor)
The mechanical treatment of solids is one of the most common and widely used operations. The volume of solids subjected to chemical treatment is very large too. Therefore, combining these two ways into one seems to be a logical solution. This method is called the mechanochemical processing of materials. Processing materials in this way has many advantages. On the one hand, this processing is economically as well as technologically feasible. Even the materials that not react together in conventional way can be prepare in this way. The mechanochemistry/mechanochemical synthesis utilizes the mechanical energy to activate chemical reactions and structural changes. The aluminothermic reduction reactions induced by the high – energy ball milling are gaining importance because of the potential applications like the synthesis of microcrystalline and nanocrystalline in – situ metal matrix composites. The mechanical activation of the chemical reactions by high energy ball milling often changes the reaction mechanism and produces metastable materials. Changes of reaction mechanisms during mechanical alloying on four different systems were studied. The system was based on this composition: Al - B2O3 - X (X = C, Ti, Nb, Cr). The possibility of another in – situ reactions during spark plasma sintering process (SPS) was also investigated. All systems were mechanically alloyed under the same conditions. After alloying, on each system scanning electron microscopy was performed and qualitative and quantitative analysis was performed using X-ray diffraction. The indentation hardness and the indentation modulus of elasticity were evaluated using nanoindentation. All analyzes were performed after mechanical alloying as well as SPS and the results were compared to each other. Based on the results, a change of reaction mechanisms was proposed for all systems. It has been found that metal matrix composites are formed and, when chromium is used, hybrid composite material reinforced with intermetallic phase and aluminum borate has been developed.
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Titanium and titanium alloys prepared by cryogenic milling
Kozlík, Jiří ; Stráský, Josef (advisor) ; Janeček, Miloš (referee)
Ultra-fine grained materials are presently thoroughly investigated due to their enhanced mechanical properties. Cryogenic milling is one of the severe plastic deformation methods, which allow production of these materials. Titanium powder was processed by cryogenic milling in liquid nitrogen and argon and consequently consolidated via spark plasma sintering method. In this work, the influence of milling conditions (liquid nitrogen vs. liquid argon, material of balls, duration and speed of milling, usage of stearic acid) on size and shape of powder particles, contamination and mechanical properties was investigated. Particle size reduction was generally not observed, while their morphology changed significantly. Using liquid nitrogen as a cooling medium leads to strong contamination of prepared material and consequently to its hardening and embrittlement. Stearic acid supresses cold welding of particles during milling and enhances its efficiency. It is possible to eliminate stearic acid from powder by cleaning in acetone before sintering, to prevent contamination of processed material. Microhardness increased, depending on milling efficiency (in liquid argon), from original 178 HV to 200-300 HV range. Increase of yield and ultimate stength was observed in compression tests while maintaining ductility....
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Unconventional methods of processing materials for knives
Bražina, Jakub ; Němec, Karel (referee) ; Doležal, Pavel (advisor)
This thesis focuses on the issue of unconvetional cutlery materials, their application for production, and the processing of a hunting knife. The readers are aquainted with cutlery issues in the search section, where the basic characteristics and properities are written. The next part describes the various metallic and non-metallic materials and their possible properities of processing and production. This thesis also deals with the surface protection of these cutlery materials. The second main part describes construction design, material selection, heat treatment, and with surface treatment of the hunting knife.
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Resonant ultrasound spectroscopy of ternary Cu-Al-Ni shape memory alloy compacts fabricated via SPS technology
Pavlík, Marek ; Spotz, Zdeněk (referee) ; Čížek, Jan (advisor)
This thesis deals with applicability of powder metalurgy for production of Cu-Al-Ni shape memory alloys. It is part of series of studies, inherently expanding experimental work with samples previously produced through optimized mechanical alloying and compaction via SPS method. In this work, the samples were thermally annealed and characterized by two advanced methods, DTA and RUS. Significant changes occur within the material at temperatures of 240 °C and 300 °C. The measurements indicated a presence of a martensitic transformation that could correspond to the desired SME phenomenon. Apparently, the changes were not triggered throughout the entire sample volume and further experimental progress is therefore expected in the near future.
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Unconventional preparation technology of bulk material from Mg
Horálek, Matyáš ; Hasoňová, Michaela (referee) ; Březina, Matěj (advisor)
Topic of the bachelor's thesis is the procedure of preparation and processing of bulk magnesium powder by unconventional technologies. Bulk materials were evaluated from the point of porosity, microstructure and physically-mechanical properties in correlation with changes of parameters during preparation. Furthemore the influence of chosen processing parameters of electron beam was evaluated from structural properties and depth of the affected material. The outcome of this work is focused on study and optimalization of parameters during preparation and processing of bulk material.
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Ternary shape memory alloys powder feedstock fabrication by advanced mechanical alloying
Regináč, Jan ; Moravčík, Igor (referee) ; Čížek, Jan (advisor)
Prášková metalurgie může být použita jako alternativní metoda pro výrobu slitin s tvarovou pamětí s Cu-bází. Tato metoda poskytla lepší výsledky, co se týče celkového složení a velikosti zrn, než tradiční metoda lití. V této práci byl aplikován proces mechanického legování k přeměně směsí základních prášků Cu-Al-Ni na mechanicky legované směsi. Cílem práce bylo nalezení optimálních parametrů pro výrobu nejvhodnějšího práškového prekurzoru určeného k dalšímu zpracování. SEM, EDX a XRD analýzy byly použity pro zjištění účinku změny parametrů na výslednou strukturu a na případnou tvorbu nových fází. Bylo ukázáno, že vysokoenergetické legování je vhodnou metodou pro výrobu takových prekurzorů. Na základě výsledků bylo zjištěno, že tuhý roztok mědi byl formován nezávisle na změně mlecích parametrů. Výsledky dále odhalily, že vysoký energetický vstup ve formě otáček a dlouhých mlecích časů, může způsobovat vznik amorfních fází.
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