In terms of reduced exhaust emissions, fuel consumption and noise, the development of combustion engines, which are more efficient and reduced in noise is of great interest for the automotive industry. In this context exhaust turbochargers play an important role because of the increasing efficiency of combustion engines as a result of recovering a part of the exhaust gas energy. Furthermore, a fast response behaviour of the turbocharger is requested, which can be realized by decreasing weight, i.e. decreasing the moment of inertia. Because of low specific weight, high strength, high stiffness and good oxidation resistance even at high temperatures, titanium aluminide (TiAl-) alloys count as an alternative class of materials to substitute heavy Ni-based alloys. The TiAl-alloys investigated in this thesis were processed using pre-alloyed powder and consolidated by hot-isostatic pressing and conventional sintering, respectively. As a reference, a cast and forged fine-grained sample was used. First a basic characterization of all TiAl-variations was made using optical microscopy, scanning electron microscopy, X-ray diffraction and hardness measurements according to Vickers. Afterwards the influences of impurities from the powder metallurgical process on the phase diagram and phase transformations were investigated using heat treatment studies, differential scanning calorimetry and thermodynamic calculations via Thermo-Calc in a comparative way. On the basis of these observations the effects of each production method on the final microstructure and its properties were determined.