The Effect of Zirconium on Titanium Aluminides

As the efficiency and, therefore, the environmental sustainability of processes increases with increasing temperatures, the development of light-weight, high-strength materials which can withstand those demanding conditions is necessary. The high melting point, low density, high specific stiffness and yield strength as well as the good creep and oxidation properties of intermetallic titanium aluminide (TiAl) alloys, make them attractive candidates for high-temperature applications in aerospace, automotive and power industries. Crucial for further alloy and processing development is controlling the deformation mechanisms, which are predominantly concentrated in the occurring γ(TiAl)-phase. Hence, it is necessary to find ways to increase the strength of this phase with methods such as solid solution strengthening. Zr is an interesting candidate to act as solid solution strengthening element. In this master thesis differential scanning calorimetry has been combined with thermodynamic calculations and heat treatment studies to establish the effect of Zr on the binary Ti-Al phase diagram. The strong γ stabilising effect has been confirmed as well as the reduction of solidus and liquidus temperature. Nanoindentation experiments were also conducted and have found a solid solution strengthening effect of Zr. All results were compared and discussed with regard to an alloy containing the already well research element Nb.