The TNM-alloy became a promising material in jet engines for the aviation industry thanks to long lasting efforts in the sector of research and development. The TNM-alloy stands out due to the good mechanical as well as thermal properties (fracture toughness, strength, creep resistance), but mostly due to a low density, so to be a lightweight option to the usually used Ni-based superalloys. Because the mechanical properties of TNM-alloys are controlled by microstructure, this has to be analysed properly and efficiently to ensure the quality of the alloy. The purpose of this work is to determine the phases present within the microstructure (α2/γ-colonies, βo, γg), as well as the γ-solvus-temperature (TγSolv) by means of heat-treatment studies. TγSolv is an important process temperature, with which the microstructure and hence the mechanical properties can be adjusted. To analyse the microstructure, quantitative metallography and X-ray diffraction experiments are used. While the first method analyses the proportion of the microstructure, the Rietveld analyses result in the fraction of the existing phases in the alloy (α2, βo, γ). In a series of experiments several cooling treatments have been done, trying to preserve the high-temperature structure in the TNM-samples, so that no lamellar precipitation of γ within the α2-grains can occur. The purpose here is to determine the globular γg-fraction by XRD, too. Another part of this work deals with texture-analysis to determine the preferred orientations in the forged TNM-samples. This information is used for analysing the XRD-pattern by means of the Rietveld-method.