Number of found documents: 2
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INFLUENCE OF MELTING TEMPERATURE AND TIME ON THE OXYGEN CONTENT IN TiAlNb ALLOYS
Barták, Tomáš; Zemčík, L.; Dlouhý, Antonín
2011 - English
The present study investigates a cost-effective melting of TiAlNb intermetallics in a stable yttrium oxide refractory. We identify mechanisms that mainly contribute to the oxygen pick-up during melting. Systematic microstructural and chemical analysis provided evidence that erosion and dissolution of crucible wall are key factors of the process. Experiments were performed using two Ti46Al7Nb alloys with a different initial content of oxygen. The alloys were re-melted in vacuum induction furnace inside U-shaped yttria crucibles. The experiments involved three different temperatures in combination with melting times spanning from 300 to 1800 s. The oxygen content of re-melted and solidified alloys was assessed by means of inert gas fusion technique. Results of the chemical analysis provided clear evidence that the stability of the refractory wall in contact with the molten alloy and its rate of dissolution depend mainly on melting temperature. These results are further supported by microstructural observations that confirmed ever growing content of ceramic phases in the solidified intermetallic with increasing temperature of the melt. The work also contributed to the improved experimental methodology, in particular to temperature measurements of reactive melts. Keywords: intermetallics; meeting; oxygen content Fulltext is available at external website.
INFLUENCE OF MELTING TEMPERATURE AND TIME ON THE OXYGEN CONTENT IN TiAlNb ALLOYS

The present study investigates a cost-effective melting of TiAlNb intermetallics in a stable yttrium oxide refractory. We identify mechanisms that mainly contribute to the oxygen pick-up during ...

Barták, Tomáš; Zemčík, L.; Dlouhý, Antonín
Ústav fyziky materiálů, 2011

METALLURGY AND PROPERTIES OF ADVANCED NiAl-Mo EUTECTICS
Barták, Tomáš; Kuchařová, Květa; Záležák, Tomáš; Dlouhý, Antonín
2010 - English
A NiAl-Mo eutectic alloy was melt from 99,99% purity components and cast by the drop casting technique. The drop-cast ternary alloy (nominal composition of Ni-45Al-9Mo at. %), was re-melted and directionally solidified using a high temperature optical floating zone furnace. A resulting in-situ composite consists of Ni-45,2Al matrix and Mo-10Al-4Ni fibers, all in at. %. The volume fraction of 14% Mo-fibers stems from the eutectic composition. Backscatter diffraction shows that the NiAl-matrix and the Mo-fibers are both < 001 >-oriented with respect to the axis of the cylindrical rods. Preliminary creep experiments confirmed an immense improvement of high temperature strength due to the fine distribution of Mo-fibres. The amount of strengthening in terms of minimum creep rate can be as high as 7 orders of magnitude. Post-mortem transmission electron microscopy experiments provided evidence that creep in the temperature range of 800 - 900 degrees C results in an extensive formation of subgrain boundaries. The strengthening effect is very likely associated with the reactions between subgrain boundaries and fine Mo-fibres. Keywords: eutectics; directional solidification; composite Fulltext is available at external website.
METALLURGY AND PROPERTIES OF ADVANCED NiAl-Mo EUTECTICS

A NiAl-Mo eutectic alloy was melt from 99,99% purity components and cast by the drop casting technique. The drop-cast ternary alloy (nominal composition of Ni-45Al-9Mo at. %), was re-melted and ...

Barták, Tomáš; Kuchařová, Květa; Záležák, Tomáš; Dlouhý, Antonín
Ústav fyziky materiálů, 2010

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