Dresden 2011 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 16: Structural Materials
MM 16.3: Vortrag
Dienstag, 15. März 2011, 11:30–11:45, IFW D
Energetics of TiAlNb alloys with interstitial carbon — •Dominik Legut1,2, Juergen Spitaler1,2, Pasquale Pavone1,2, and Claudia Ambrosch-Draxl1 — 1Atomistic Modelling and Design of Materials, Leoben, Austria — 2Materials Center Leoben, Leoben, Austria
TiAl based alloys exhibit attractive properties such as low density, high strength at high temperatures, and very good oxidation resistance. However, they are brittle at room temperature. It was recently found that lamellar structures, obtained by alternating the γ and α2 phase, addition of transitional metal or interstitial elements like carbon increase ductility and creep strength at room temperature.
We perform first-principles calculations based on density-functional theory to study the influence of interstitial carbon on the energetics of both the γ and α2 phase of the TiAlNb alloy system, where Nb atoms substitute Ti sites. In particular, we determine the heats of formation with respect to the pure TiAl phases, taking into account various configurations for the substitutional Nb sites. In our calculations, the carbon atoms are located on one of two possible interstitial sites.
We consider two different situations. First, Al-rich systems are obtained by replacing Ti atoms with Nb. Second, in Ti-rich systems, the concentration of Ti atoms is kept constant (50%) by moving the Ti atoms replaced by Nb to Al sites. We find that in all cases the energy cost of accommodating carbon is very much affected by the presence of the alloying element Nb.