The understanding of residual stresses is essential to utilize materials properties and to optimize castings. Previous experiments showed a large deviation between simulated and determined residual strains and stresses in composite castings. These can be traced back by the fact that time- and temperature-dependent material behavior like stress relaxation or creep is not considered by commercial simulation. Heat treatment commonly follows the casting process. It also affects residual stresses and shows stress relaxation. In order to understand these effects along the process chain stress relaxation will be analyzed during heat treatment of the casting. A composite component - similar to in-cast cylinder liners in a motor block - will be analyzed in-situ and ex-situ. The results will enable us to optimize residual stress simulation for temperature-dependent manufacturing processes.