The current article focuses on recent work done in understanding the role of processing techniques on interface evolution and connecting interface evolution to interface thickness-dependent properties. Special emphasis is placed on interface evolution during the sintering process of tungsten (W). Sintering with additives such as nickel significantly changes grain boundary properties in W, leading to issues such as grain boundary embrittlement. When one has to mechanically describe properties of polycrystalline W with an account of the influence of grain boundary embrittlement, one must explicitly consider grain boundary properties. This issue is the focus of the present work on the mechanical properties of interfaces. Overall, a phase field modeling-based approach is shown to be an excellent computational tool for predicting the interface evolution. The influences of the interface thickness, chemistry, and orientation of phases around interfaces are analyzed using extended finite element simulations for polycrystalline W. © 2016, The Minerals, Metals & Materials Society.