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Influence of heat treatment on deformation behaviour of wrought Mg-Zn-based alloys
Olejňák, Juraj ; Drozdenko, Daria (advisor) ; Mathis, Kristián (referee)
Title: Influence of heat treatment on deformation behaviour of wrought Mg-Zn alloys Author: Juraj Olejňák Department: Department of Physics of Materials Supervisor: RNDr. Mgr. Daria Drozdenko, Ph.D. Abstract: The aim of the present thesis is to understand an influence of heat treatment on microstructure and mechanical properties of extruded Mg-Zn based alloys containing an addition of Ca and Nd. Microstructural analysis provided by electron microscopy gave us information about homogeneity and distribution of precipitates in investigated Mg alloys after extrusion and a subsequent heat treatment. Microhardness and compression test along the extrusion direction have been performed to determine optimal aging conditions for achieving better mechanical properties, such as hardness and strength. The acoustic emmision technique was used to follow active deformation mechanisms during plastic deformation. Application of the acquired knowledge in material research can contribute to design novel Mg alloys with enhanced mechanical properties for specific applications. Keywords: magnesium alloys, isothermal aging, precipitation, mechanical properties
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Mechanical properties of pre-compressed Mg-Zn-Ca alloy
Hegedüs, Marius ; Dobroň, Patrik (advisor) ; Lukáč, Pavel (referee)
In wrought Mg alloys, their hexagonal closed packed structure together with a pronounced basal texture lead to anisotropy of mechanical properties. This bachelor thesis is focused on understanding the influence of previous deformation with further relaxation and/or additional heat treatment on deformation behaviour of the extruded Mg-Zn-Ca alloy. The significant influence of twins formed after pre-compression on mechanical properties was investigated. Evolution of microstructure, especially a formation of twins, is observed by light and scanning electron microscopy. The acoustic emission technique is used to determine active deformation mechanisms: dislocation slip and twinning. The results can be used for developing Mg alloys with enhanced properties.
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Microstructure and properties of enhanced twin-roll cast aluminium alloys.
Poková, Michaela ; Cieslar, Miroslav (advisor) ; Karlík, Miroslav (referee) ; Kruml, Tomáš (referee)
Three aluminium alloys from AA3003 series modified by zirconium were pre- pared by twin-roll casting. The role of composition, heat treatment and deforma- tion by cold-rolling or equal channel angular pressing on evolution of microstruc- ture and mechanical properties were studied. High density of α-Al(Mn,Fe)Si pre- cipitates formed during annealing between 300 ◦ C and 500 ◦ C. Coherent Al3Zr particles precipitated during annealing at 450 ◦ C with slow heating rate. Recrys- tallization resistance of deformed alloys was enhanced by either Al3Zr precipitates formed before deformation or by α-Al(Mn,Fe)Si particles nucleating simultane- ously with recrystallization. 1
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Phase transformations in Mg-Gd alloys
Stíbal, Adam ; Vlach, Martin (advisor) ; Mathis, Kristián (referee)
ývoj hořčíkový h slitin má ekonomi koEekologi ké opodst-tněníF yužití tě hto slitin je n- vzestupné tenden i - z-s-huje zejmén- do tr-nsportního pr·mysluD -le svoje upl-tnění n- hází i v medi íněF tedn- z metod zlepšení vl-stností hořčíku je legování jinými prvkyF vláš¡' do rý h výsledk· dos-huje legování prvky vzá ný h zeminF "ento typ slitinD kde legují ím prvkem je g-doliniumD jsou studovány v předklád-né prá i ve tře h tl-kově litý h slitiná h do kon entr- e IS hmF7F ředmětem prá e ylo studium fázový h tr-nsforE m- í při žíhání m-teriálu pomo í metody diferenční skenov- í k-lorimetrie při neizotermi kém žíháníF fyly pozorovány tři pro íh-jí í pro esy - spočteny jeE ji h -ktiv-ční energieF "ěmto pro es·m ylo n- zákl-dě srovnání s liter-turou přiř-zeno kl-strování -tom· qd - pre ipit- e met-st- ilní h fází β - β F I
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Positron annihilation study of precipitation effects in Mg-Tb alloy
Hruška, Petr ; Čížek, Jakub (advisor) ; Vlach, Martin (referee)
Magnesium alloys are currently widely used in industry as a modern material. Magnesium based alloys with rare earth elements shows very promising mechanical properties. In the present work the precipitation effects and the deve- lopment of microstructure of the Mg13Tb alloy (containing 13 wt.% of terbium) during isochronal annealing were studied by positron annihilation spectroscopy, microhardness measurement and differential scanning calorimetry. According to the results the creation of the precipitates β′′ , β′ and β in the studied alloy was observed and activation energies of these precipitates were determined by the Kissinger method. By microhardness measurement the natural ageing at room temperature of the Mg13Tb alloy was observed and described. 1
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Advanced ceramics for tissue engineering
Vojtíšek, Jan ; Koplík, Jan (referee) ; Bartoníčková, Eva (advisor)
This bachelor´s thesis deals issues of ceramics materials suitable for tissue engineering. An artificial substitute for human tissue can be divided to several generations. This include inert, bioactive and bioresobable materials. Resorbable substitutions are prepared from materials, which could substitute host tissue, for example hydroxyapatite. HA can be prepared in different ways (dry and wet way). To better application in medicine, ceramics foams prepared by in situ foaming or replication technique are using. Experimental part of this paper deals preparing of hydroxyapatite powder and process optimization. Samples was characterized by IR and Raman spectrometry, XRD analysis and particle size was studied by SEM. Ceramics foams was prepared by in situ foaming from Al2O3, HA and composites (in ratio 50 – 50, 75 – 25, 90 – 10). Porosity was evaluated by stereomicroscope, density and level of sintering was studied by SEM microscopy.
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Structure and properties of electron beam penetration produced in steel AMS 5659
Říčan, Daniel ; Foret, Rudolf (referee) ; Kouřil, Miloslav (advisor)
This master thesis deals with the electron beam welding of the AMS 5659 steel used in industry for special hydraulic cylinders (Fig. 1). A theoretical analysis of electron beam welding and analysis of the influence of selected welding parameters on penetration characteristics are in the first part of the thesis. The second part contains an evaluation of the implemented experimental penetrations on samples of the steel in the hardened condition H1025 and after solution heat. It was also done a properties assessment of the same samples that were been hardened again. The light microscopy (SM), the scanning electron microscopy (SEM) and the measurement method of hardness according to Vickers were used for evaluation and comparison of the steel properties in the region of penetration and the heat affected zones properties.
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Synthesis of bioceramic materials based on hydroxyapatite
Kočicová, Pavla ; Králová, Marcela (referee) ; Částková, Klára (advisor)
The thesis deals with the precipitation synthesis of nanoparticle hydroxyapatite with goal to study the influence of reaction conditions on the morphology of the particles. The theoretical part is focused on biomaterials, bioceramics and phosphates characterization. Further the work is focused on hydroxyapatite, its characteristics and possible synthesis in particular. The synthesis of hydroxyapatite precipitation is described in the experimental part. Syntheses were performed at a reaction temperature of 0-80 °C at pH = 8-11, at the aging time of 0-24 h, in the presence of surfactant and the chelating agent and with the post-precipitation hydrothermal or ultrasonic treatment. For characterization of the prepared powders, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), laser diffraction (LD) and the analysis of the specific surface area (BET) were used. Pure hydroxyapatite powders or a mixture of hydroxyapatite and tricalcium phosphate were prepared by precipitation syntheses. HA particle morphology was strongly affected by the reaction temperature – with increasing temperature the larger particles with a clearer morphology were formed, mostly in the rod shape. Postprecipitation hydrothermal treatment had a significant influence on the morphology of HA particles – it caused the formation of spherical or slightly elongated particles. The reaction medium of water/ethanol significantly affected the particle morphology – it inhibited the particle growth.
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Semiconducting ceramics for thermoelectric application
Jebavá, Alžběta ; Koplík, Jan (referee) ; Bartoníčková, Eva (advisor)
This diploma thesis focuses on the syhnthesis of multicomponent ceramic system based on Ca-(Mn,Co)-O. The thesis is devided in theoretical and experimental part. The theoretical part is describing ceramic materials for thermoelectric application, preparation and synthesis of these materials and their processing. The experimental part is dealing with synthesis of ceramic powder which is processed to the porous ceramics. The properties of prepared porous ceramics are observed.
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Synthesis of ceramic powder materials in the presence of the ultrasound field
Kočicová, Pavla ; Bartoníčková, Eva (referee) ; Částková, Klára (advisor)
The thesis concerns the synthesis Ceric Oxide, Samarium Oxide and Samarium doped Cerium Oxide. The theoretical part is focused on the characteristics, applications and possibilities of the Cerium Oxide synthesis. The experimental part describes the precipitation of the Cerium Oxide powder. The synthesis of the powders were proceeded in the normal conditions or in the presence of ultrasonic field. For the purposes of description of the ready powders the x-ray diffraction (XRD) and the raster electron microscopy (SEM) were used. The ceramics were made of the selected powders where the structure was described by SEM, the density by Archimedes´Method and the grain size by grid-line intersect method. Using the precipitation synthesis, the pure powders of Ceric Oxide, Samarium Oxide and Samarium doped Cerium Oxide were prepared. The powder morphology was strongly involved by the pH level and by ageing time. The ultrasound was accelerating the ageing. At the values of pH > 11 the rodlike particles were created. The ageing time and the ultrasound supported the creation of the rodlike particles. The ceramics made of the powder with the presence of the rodlike morphology showed the density up to 97,14% of the theoretical density.
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