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National Repository of Grey Literature 3 records found  Search took 0.01 seconds. 
Microstructure and mechanical properties of ultra-fine grained titanium alloys
 Václavová, Kristína ; Stráský, Josef (advisor)
Title: Microstructure and mechanical properties of ultra-fine grained titanium alloys Author: Bc. Kristína Václavová Department / Institute: Department of Physics of Materials Supervisor of the master thesis: PhDr. RNDr. Josef Stráský, Ph.D. Abstract: Metastable β-Ti alloys Ti-15Mo and Ti-6.8Mo-4.5Fe-1.5Al (TIMETAL LCB) were subjected to severe plastic deformation by high pressure torsion. Microhardness of Ti-15Mo and TIMETAL LCB alloys increases with increasing inserted deformation, i.e. with increasing number of HPT rotations and also with increasing distance from the centre of the sample. The highest microhardness after HPT exceeds significantly the microhardness of two-phase α + β heat-treated material. Increasingly deformed microstructure was also demonstrated by scanning electron microscopy and by electron back-scattered diffraction (EBSD). Significant twinning was observed in both studied alloys. Mechanism of multiple twinning contributes notably to the fragmentation of grains and thus to the refinement of the microstructure. Defect structure in Ti-15Mo alloy was studied by positron annihilation spectroscopy. It was proved that dislocations are the only detectable defects in the material by positron annihilation spectroscopy and that dislocation density increases with the number of HPT revolution and...
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Microstructure and mechanical properties of ultra-fine grained titanium alloys
 Václavová, Kristína ; Stráský, Josef (advisor)
Title: Microstructure and mechanical properties of ultra-fine grained titanium alloys Author: Bc. Kristína Václavová Department / Institute: Department of Physics of Materials Supervisor of the master thesis: PhDr. RNDr. Josef Stráský, Ph.D. Abstract: Metastable β-Ti alloys Ti-15Mo and Ti-6.8Mo-4.5Fe-1.5Al (TIMETAL LCB) were subjected to severe plastic deformation by high pressure torsion. Microhardness of Ti-15Mo and TIMETAL LCB alloys increases with increasing inserted deformation, i.e. with increasing number of HPT rotations and also with increasing distance from the centre of the sample. The highest microhardness after HPT exceeds significantly the microhardness of two-phase α + β heat-treated material. Increasingly deformed microstructure was also demonstrated by scanning electron microscopy and by electron back-scattered diffraction (EBSD). Significant twinning was observed in both studied alloys. Mechanism of multiple twinning contributes notably to the fragmentation of grains and thus to the refinement of the microstructure. Defect structure in Ti-15Mo alloy was studied by positron annihilation spectroscopy. It was proved that dislocations are the only detectable defects in the material by positron annihilation spectroscopy and that dislocation density increases with the number of HPT revolution and...
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Experimentální studium ultrajemnozrnných slitin Ti pro využití v biomedicíně
 Václavová, Kristína ; Stráský, Josef (advisor) ; Šíma, Vladimír (referee)
In the present work the microstructure evolution of Ti-6Al-7Nb alloy prepared by high pressure torsion (HPT) and equal channel angular pressing (ECAP) was studied by scanning electron microscopy, microhardness measurements and electrical resistance measurements. Electron microscopy showed a bimodal structure of the alloy and deformed structure after HPT. Microhardness increased with the increasing number of turns of high pressure torsion. Electron back-scattered diffraction figured out that the grain misorientations are not random. Changes in the electrical resistance of the alloy prepared by ECAP showed irreversible process after heating above 450řC.
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