Copper based materials are of huge importance for modern society. Their mechanical and and electrical properties are determined by their chemical composition as well as by the thermo-mechanical treatment during production. X-ray diffraction is a simple and cost-efficient method to in-situ evaluate the properties of copper based materials during thermal treatment. The analysis of peak profiles for the high temperature X-ray diffraction is addressed in this work. Thereto the conventional Rietveld-Method is extended by a global mathematical optimization method (simulated annealing). Optimization techniques as well as procedures for splitting K-alpha-peaks in diffractogramms are implemented in the coding language Fortran. Furthermore, high temperature X-ray experiments were performed on cold-rolled copper samples in co-operation with Anton Paar GmbH. The programmed software is used to simulate the experimentally obtained diffractograms. Thereby the microstrains in the samples were analyzed. The dislocation densities are deduced from the microstrain. The microstrains are not adequately described by Williamson-Hall plots. By means of extended Williamson-Hall plots, where the anisotropy of the elastic strain field is considered, the peak broadening can be described as a function of the peak position.