In order to optimize the properties of engine disks through the forging process at voestalpine BÖHLER Aerospace GmbH & Co KG, a model was developed to predict the microstructure characteristics of Rene 65 turbine disks. This model, coupled to a finite element simulation, is able to predict grain sizes and their distribution (e.g. duplex) in ASTM grain classes at every point of a component. Furthermore, the model describes the recrystallization behavior of the material and predicts it’s mechanical properties. The alloy Rene 65 is composed of a fcc γ matrix with coherent γ’ precipitates (L₁₂ structure), which mainly influence the strength as well as the grain size of this material. The recrystallization behavior was modeled by recording flow curves at temperatures around the γ' solvus temperature and characteristic strain rates for the used forging equipment. To validate the results, existing geometries of engine disks were produced and compared with the simulation results by means of microstructural and mechanical properties. The evaluation of scanning electron microscopy images including electron backscatter diffraction were used to analyze additional properties such as the local dislocation densities as well as the size and distribution of γ' and other precipitates. Special focus in the development of the model is laid on the adjustment of the grain size of the γ phase and in the distribution and size of the γ' precipitates, which has the greatest impact on the high strength of Rene 65 turbine disks. In the development of next generation engines with highest efficiencies, this simulation tool can be used to optimize the properties of rotating parts at elevated temperatures and adapt the thermo-mechanical processes to achieve unique properties.