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The Study of Phase Transformation in Titanium Alloys
Zháňal, Pavel ; Harcuba, Petr (advisor) ; Kalvoda, Ladislav (referee) ; Strunz, Pavel (referee)
In this work phase transformations in metastable β (primarily Ti-15Mo) alloys were studied utilizing electrical resistance, dilatometry, transmission electron microscopy and X-ray and neutron diffraction. The materials Ti-15Mo, Ti-6.8Mo-4.5Fe-1.5Al (LCB), Ti-5Al-5V-5Mo-3Cr (Ti-5553), Ti-29Nb-1Fe-0.5Si (TNFS), Ti-15Mo-3Nb-3Al-0.2Si (Timetal 21S) and Ti-13Cr-1Fe-3Al (TCFA) (in wt. %) - were subjected to a solution treatment at a temperature above β transus and quenched into water. In this condition, the microstructure of the investigated materials consists of β matrix and ω particles. Samples quenched from important temperatures determined from in-situ electrical resistance and dilatometry measurements were studied by post-mortem TEM. In-situ X-ray and neutron diffraction provided direct observations of microstructure of Ti-15Mo alloy during linear heating and confirmed statements based on results of indirect methods, such as: the decrease of volume fraction of ω phase during heating at low temperatures (up to 250 ◦ C), complete dissolution of ω phase at 560 ◦ C and precipitation of α phase without ω particles serving as its direct precursors. X-ray diffraction experiment allowed to determine relative evolution of the size of ω particles while phase fraction evolution was derived from neutron diffraction. The...
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Biocompatibility of transition metal alloys: physical-chemical background
Rafaj, Zdeněk ; Nehasil, Václav (advisor) ; Kolářová, Tatiana (referee)
Titanium alloys are widely used for manufacturing of bone implants. Recent studies proved superior mechanical and chemical properties of TiNb alloys. The performance of TiNb is analyzed on Ti39Nb alloy and on evaporated layers of Ti, Nb and TiNb. Performance is compared to Ti6Al4V and pure Ti. This work is focused on the early stage of a bone growth process (studied in vitro). An investigation of this early stage has not been found in any available literature. At this early stage, CaHPO4 compound is formed. This compound is accompa- nied by Mg oxide formation. It is a difference to later stage of this process (as observed in many studies) where the layer is created solely by hydroxylapatite, Ca10(PO4)6(OH)2. The thermal oxidation of surface leads to a grain structure and to a rougher surface. The surface with different roughness effects growth rate depending on material. Generally, the best performance is achieved with TiNb (only polished as well as subsequently thermally oxidized), followed by Ti. 1
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