Results for “TiAl2O5”

DOE OSTI2020

Materials Data on TiAl2O5 by Materials Project

Al2TiO5 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ti4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ti–O bond distances ranging from 1.85–2.17 Å. Al3+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 29–51°. There are a spread of Al–O bond distances ranging from 1.85–2.11 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to one Ti4+ and three equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing OTiAl3 trigonal pyramids. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Ti4+ and two equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ti4+ and two equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗

NASA NTRS1992

Thermodynamics, Solubility, and Diffusivity of Oxygen in Titanium and Ti-Al Alloys

Titanium aluminides and titanium aluminide-based composites are attractive candidate materials for high-temperature structural applications. As these materials may be exposed to oxidizing environments durine their use at elevated temperatures, it is essential that they possess a good oxidation resistance. Previous studies have shown that the oxidation resistance of Al-rich alloys in the Ti-Al system is superior to that of the Ti-rich alloys. The scales formed on the surface of the Al-rich and Ti-rich alloys have been reported to be predominantly Al2O3 and TiO2, respectively. Since the relative stabilities of the oxides of Al and Ti at various temperatures and oxygen pressures can be assessed from their thermodynamic data, it is possible, With the help of thermodynamic calculations, to determine the compositions of the alloys which would form scales of Al2O3, TiO(x) or a ternary oxide such as TiAl2O5 during oxidation at a given temperature. The thermodynamic calculations require reliable activity data for the Ti-Al system. These data have not been determined for the entire composition and temperature range of interest. Using the data available in the literature, recently performed thermodynamic calculations and concluded that the stable oxide changed from TiO to Al2O3 in the existence region of the tial phase. In the case of titanium aluminide-based composites, another major concern is the mutual chemical compatibility of the matrix material with the reinforcement phase. Fibers of SiC, TiB2 and Al2O3 are currently being investigated for reinforcement of titanium aluminide matrices.

Mehrotra, Gopal M.↗