In this presentation, we review our recent efforts in developing computational models and constitutive equations for beta grain growth during beta-annealing, thickening of grain boundary alpha, growth and dissolution of primary alpha and formation of sideplates during thermal processing of Ti-6Al-4V. The simulation techniques employed include phase field method and DICTRA method, with fundamental model inputs linked to CALPHAD thermodynamic database and diffusivity database. For beta grain growth, the dependence of grain boundary energy and mobility on misorientation has been incorporated into the phase field model and systems consisting of different textures in the initial microstructure have been considered. The constitutive equations developed have been validated against both computer simulations and experimental observations. The work is supported by AFRL under MAI grant P035558.