Advanced intermetallic γ-TiAl-based alloys of the 4th generation are used in aircraft engines and automotive applications due to their low density and outstanding high-temperature properties. An example of such innovative γ-TiAl-based alloys is the so-called TNM alloy with a nominal composition of Ti-43.5Al-4Nb-1Mo-0.1B (in at.%). TNM alloys are complex structured, multi-phase alloys, which consist mainly of γ-TiAl, α2-Ti3Al and small amounts of βo-TiAl phase. This type of alloys, which solidify via the β-phase, show an almost segregation-free solidification structure with small average grain size. After casting and hot-isostatic pressing, however, a small fraction of the grains exhibit large sizes and adverse shapes, thus representing internal notches which may initiate cracks under tensile loading and thereby significantly decrease the materials ductility at room temperature. In these investigations, the potential of refining coarse grains, i.e. to mitigate potential crack-initiation sites, and thus to homogenize the microstructure by means of special heat treatments is assessed. An ensuing heat treatment step targets to adjust balanced mechanical properties. After each heat treatment step, microstructures were characterized by means of light optical and scanning electron microscopy as well as hardness measurements. Optimized heat treatments were proposed for planned tensile tests. Differential Scanning Calorimetry (DSC) was used to verify the phase diagram. In the second part of the work, basic examinations of carbonaceous TNM+C alloys were carried out. The aim of the carbon addition is to increase the maximum operating temperature and to set a property improvement in strength and creep resistance. Microstructures of the cast and hot-isostatically pressed TNM+C alloys were examined for homogeneity through light and scanning electron microscopy. Energy dispersive X-ray analysis and X-ray diffraction studies were used to determine the occurring phases. Hardness tests were applied to detect an expected increase in hardness. By means of DSC measurements, transformation temperatures of the alloy variants were determined and a possible change of the solidification path by the addition of carbon was investigated.