Abstract
Titanium aluminides are considered to be the future high-temperature structural materials for turbine applications. Major focus is on α2Ti3Al based and γTiAl based alloys. Niobium additions to Ti3Al alloys is found to improve the room-temperature ductility. Thus phase equilibria in Ti-Al-Nb system is of practical significance with regard to their processing and high-temperature phase stability characteristics. In the present research, four alloys with compositions Ti-22Al-12Nb, Ti-21A1-16Nb, Ti-20Al-20Nb, and Ti-25Al-25Nb (all in atom percent) were equilibrated at 1000 °C for 225 hours and then quenched in water. The quenched alloys were characterized for phase relations by optical microscopy, X-ray diffraction (XRD), and electron probe microanalysis (EPMA). Based on the phase analysis, the ternary isotherm of the Ti-Al-Nb system at 1000 °C was constructed on the Ti3Al-rich side. The orthorhombic Ti2AlNb phase was observed in the sample with Ti-25Al-25Nb composition signifying the presence of this phase at 1000 °C.
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Kumar, S.G., Reddy, R.G. & Brewer, L. Phase equilibria in Ti3Al-Nb alloys at 1000 °C. JPE 15, 279–284 (1994). https://doi.org/10.1007/BF02669217
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DOI: https://doi.org/10.1007/BF02669217