Calculation of unary and multicomponent phase diagrams from thermodynamic data or solution models. Fundamental mechanisms of diffusion and the importance of processing conditions, notably temperature, and microstructural features such as grain boundaries, dislocations, and surfaces, on the total transport in a material. Role of the thermodynamic driving force for diffusion, and alternative treatment of diffusion in terms of an appropriate gradient in potential. How driving forces of varying types and barriers due to surface energy effects interact to dictate the rate of phase transformation and microstructural change.