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2 Zeszyty Naukowe. Mechanika / Politechnika Opolska

2 2010

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The study of properties TiAl-Nb alloys

Juřica J., Losertová M., Petlák D.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2010

z. 97

8-8

Subject of this work is an intermetallic alloy based on TiAl and doped with Nb with high creep resistance and good mechanical properties. The experimental Ti-Al-Nb material with two compositions of Ti-45Al-10Nb and Ti-40Al-15Nb was prepared from master alloy TiNb (55/45 wt. %) and Al pieces by plasma melting, vacuum induction remelting and casting into the rod shape. The samples were homogenisation annealed at 1100°C for 12 hours in Ar atmosphere and water quenched from 700°C. Heat treatment at 700 °C for 8 hours in Ar atmosphere as well as in hydrogen flowing gas was realised to prepare experimental material for hydrogen effect study. Microstructure of the specimens was studied by light and scanning electron microscopies, microhardness measurement and phase microanalysis were performed. The lamellar microstructure of the samples in as-cast and heat treated conditions formed of the ? (45 at.% Al) and ?2 (41 at.% Al) phases resulted from metallographic observation and EDS phase analysis. Microhardness values of the samples decreased after annealing and quenching. Effect of hydrogen on lamellar microstructure and microhardness values was studied on the hydrogen-charged and hydrogen-free specimens. X-ray diffraction analyses were performed on Ti-Al-Nb specimens.

The study of microstructure TiNb based alloys with different heat treatment

Štěpán P., Losertová M., Petlák D.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

2010

z. 97

33-33

The study of TiNb-based alloys that are suitable candidates for substitution of TiNi in many biocompatible applications was performed. The experimental alloys with two nominal compositions Ti22Nb and Ti25Nb (at.%) were prepared by plasma melting of TiNb master alloy (55/45 wt.%) and Ti pieces. Different conditions of heat treatment were performed and consisted of homogenisation annealing at 1100°C for 12 hours in flowing Ar gas and water quenching and solution annealing at 900°C for 1 hour in flowing Ar gas and water quenching followed by precipitation aging at different temperatures (200, 400 and 600°C) for 1 hour. The metallographic observation and phase microanalysis of the alloys proved the composition homogeneity. The microstructure of Ti22Nb and Ti25Nb samples after plasma melting was dendritic with very fine martensite needles. After solid solution annealing of plasma melted alloys, the presence of ? phase and " martensite in the microstructure was observed. The microhardness values showed obvious relation with heat treatment and aging. The annealing at 1100°C and quenching increased microhardness because the dendritic and martensite microstructure changed to lamellar one. Furthermore, the higher Nb content in Ti25Nb alloy decreased microhardness of the samples in plasma melted as well as annealed conditions by reason of increasing amount of beta phase.