Ti-6Al-4V is common material for additive manufacturing. However, parts formed by Selected La-ser Melting are known to be brittle so that a post-process heat treatment is required. One important goal for this additional production step is the degeneration of the martensitic ´-phase that had formed by the extreme conditions during layer-wise production. By using a phase-field based soft-ware that couples thermodynamic information with a diffusion solver to get a spatially resolved phase transformation description, we have investigated the microstructural dynamic of heat treat-ment procedures typical for additive manufactured Ti-6Al-4V parts. The model describes modifica-tion of the grain sizes and shapes, evolution of phases, and corresponding concentration distribu-tions during phase transition induced by annealing.