National Repository of Grey Literature 29 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Beta-Ti alloys for medical applications
Preisler, Dalibor ; Stráský, Josef (advisor) ; Karlík, Miroslav (referee) ; Caram jr., Rubens (referee)
1 Title: Beta-Ti alloys for medical applications Author: Dalibor Preisler Department / Institute: Department of Physics of Materials Supervisor of the doctoral thesis: doc. PhDr. RNDr. Josef Stráský, Ph.D., Department of Physics of Materials Abstract: Interstitial strengthening by a high amount of oxygen can be used in metastable beta-Ti alloys, for achieving very high strength without compromising ductility. The content of oxygen however influences the phase stability and consequently increases the Young's modulus. Several alloys with various content of beta-stabilizing elements were prepared by common metallurgical route. On top of that, dozens of compositions were prepared by a high-throughput powder metallurgy method and thoroughly studied. Lattice softening due to proximity to a martensitic transformation was utilized to minimize the Young's modulus. Effect of omega phase was thoroughly studied; it was found that the embrittlement by the athermal omega phase is most probably connected with the high oxygen content and its room-temperature diffusion into omega particles. Fundamental difference between elastic behaviour of alloys containing a significant fraction of omega and those with only a limited amount of omega was demonstrated. Regarding the plastic deformation mechanisms, it was found that...
Fracture behavior of FeAlSi intermetallics
Čech, J. ; Haušild, P. ; Karlík, M. ; Nová, K. ; Průša, F. ; Novák, P. ; Kopeček, Jaromír
The study is devoted to the intermetallic alloy FeAl20Si20 (wt.%) with the potential applications in high temperature aggressive environments. The samples of the same chemical composition were prepared by spark plasma sintering from the different mechanically alloyed powders (pure elements and pre-alloyed powders).
Microstructure of non-equiblirium Al-Mn based solid solutions
Poková, Michaela ; Cieslar, Miroslav (advisor) ; Karlík, Miroslav (referee)
Heat exchangers in automotive industry are often manufactured from aluminum-based alloy AW 3003. In recent time, the aim to reduce the weight of the cars leads to thickening of the foils, which are used for manufacturing of the heat exchangers. In order to fulfill all requirements on mechanical properties of the exchanger, new materials and thermo-mechanical treatments have to be found. Modified alloy AW 3003 with addition of zirconium seems to be perspective. Zirconium forms metastable precipitates Al3Zr, which pin moving grain boundaries and shift recrystallization to higher temperatures. The most effective heat treatment, which leads to precipitation of these particles, seems to be a two-step annealing at temperatures 250 řC and 450 řC with slow heating rate. The precipitates formed were of diameter 10 nm.
Complex investigation of fine-grained polycrystals of Cu and CuZr alloy processed by equal channel angular pressing a high pressure torsion
Srba, Ondřej ; Janeček, Miloš (advisor) ; Hadzima, Branislav (referee) ; Karlík, Miroslav (referee)
Title: Complex investigation of fine-grained polycrystals of Cu and CuZr alloy processed by equal channel angular pressing and high pressure torsion Author: RNDr.Ondřej Srba Department: Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University Prague Supervisor: Doc. RNDr. Miloš Janeček, CSc. Abstract: In the thesis the microstructure development, mechanical, elastic and corrosion properties of deformed specimens of pure Cu and binary alloy CuZr processed by equal channel angular pressing (ECAP) are investigated. Several properties of pure Cu processed by ECAP are compared with properties of the same material processed by high pressure torsion (HPT). The microstructure development is characterized in detail by several experimental techniques (light and electron microscopy, electron back scatter diffraction, positron annihilation spectroscopy, etc.). The microstructure development in specimens processed by ECAP is characterized by the continuous fragmentation of the initial coarse grain structure and the formation of new grains having the sizes in the submicrocrystalline range (of 460 nm and 260 nm in Cu and CuZr alloy, respectively). During the deformation by ECAP the fraction of high-angle grain boundaries, the dislocation density and the concentration of vacancies are...
Study of deformation processes in hexagonal materials
Čapek, Jan ; Mathis, Kristián (advisor) ; Karlík, Miroslav (referee)
The deformation mechanisms of commercially pure magnesium using advanced in-situ methods were investigated in the present work. Compression and tensile test were done at room temperature. Simultaneously, the neutron diffraction was measured and the acoustic emission was recorded. The microstructure of the deformed material was also studied by means of optical microscopy and electron back-scattered diffraction. These measurements provided information about twin nucleation and growth, microstructure changes and the influence of the orientation of grains on the number of twins and their shape. The values obtained were compared to the Elasto-Plastic Self-Consistent model, which provides information about the activity of deformation mechanisms. We focused on clarifying the influence of twinning activity on asymmetry between tensile and compression deformation.
Effect of implantation of C, Si and Cu into ZrNb nanometric multilayers
Daghbouj, N. ; Karlík, M. ; Lorinčík, J. ; Polcar, T. ; Callisti, M. ; Havránek, Vladimír
Sputter-deposited Zr/Nb nanometric multilayer films with a periodicity (L) in the range from 6 to 167 nm were subjected to carbon, silicon and copper ion irradiation with low and high fluences at room temperature. The ion profiles, mechanical proprieties, and disordering behavior have been investigated by using a variety of experimental techniques (Secondary Ion Mass Spectrometry - SIMS, nanoindentation, X-ray diffraction - XRD, and scanning transmission electron microscopy - STEM). On the STEM bright field micrographs there is damage clearly visible on the surface side of the multilayer. Deeper, the most damaged and disordered zone, located close to the maximum ion concentration, was observed. The in-depth C and Si concentration profiles obtained from SIMS were not affected by the periodicity of the nanolayers. This is in accordance with SRIM simulations. XRD and electron diffraction analyses suggest a structural evolution in relation to L. After irradiation, Zr (0002) and Nb (110) reflexions overlap for L=6 nm. For the periodicity L > 6 nm the Zr (0002) peak is shifted to higher angles and Nb (110) peak is shifted to lower angles.
Analysis of twin-roll cast aluminium-steel clad strips
Křivská, Barbora ; Šlapáková, Michaela (advisor) ; Karlík, Miroslav (referee)
The microstructure, diffusion and phase transformations in aluminum-steel clad sheet were studied within the thesis by means of light optical microscopy, electron microscopy, resistometry and positron annihilation spectroscopy. Results of experimental methods were supplemented by finite element method employed for evaluation of electrical resistivity and simulation of diffusion between steel and aluminum. Several annealing experiments were carried out. The effective interdiffusion coefficient was evaluated by Boltzmann-Matano method from measured concentration profiles through the interface. Formation of an interfacial intermetallic phase was studied and orthorhombic phases Al13Fe4 and Al5Fe2 were identified present in the layer. Surprising results were obtained from the in-situ annealing in TEM (SEM) which go against the results found in a recent literature - the interfacial layer grows towards steel layer.
State-owned enterprise and its property
Karlík, Martin ; Horáček, Vít (advisor) ; Eichlerová, Kateřina (referee)
Over the last 20 years the number of state-owned enterprises has been steadily declining. At this point there are only about 40 active state-owned enterprises and even greater number of inactive state-owned enterprises which are currently in phase of liquidation. Despite the slim numbers of active state-owned enterprises their role in economy remains still important especially as way how to participate in business activities with state owned property. State-owned enterprises manage property in value of approximately 170 billion Czech crown and using this property they are able to achieve profit over 7.5 billion Czech crown every year. The most important source of legislation regarding state-owned enterprises is act. No. 77/1997 Coll., state-owned enterprises act, which has been amended eleven times. Very important amendment was act No. 213/2013 Coll. which introduced a mechanism that allows to transfer a part of state-owned enterprise profit to state budget. Nevertheless the most important amendment is act No. 253/2016 Coll. with effect from 01. 01. 2017 which in reaction to recodification of private law in Czech Republic and insufficient regulation of some areas introduces substantial chances. The biggest changes are introduced in the area of disposition with state property. The new amending act...

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