Phase transformations in high niobium and carbon containing γ-TiAl based alloys

Phase transformations and phase transition temperatures in Ti–45 at.%Al alloyed with different amounts of niobium and carbon were investigated. Scanning electron microscopy, electron back-scattered diffraction and differential scanning calorimetry were applied for the characterisation of the prevailing phases and phase transformations. Both, niobium and carbon display a tendency to increase the eutectoid temperature, with carbon showing the stronger effect. In contrast, the influence of niobium and carbon on the α-transus temperature is rather small. Thermodynamic equilibrium calculations were performed with the aid of the software ThermoCalc and MatCalc on the basis of a commercially available TiAl database. Partly, the calculated data show significant differences when compared to experimental results.