A novel model of third phase inclusions on two phase boundaries

A new computationally efficient model of an included phase located at the interface between two other phases is developed by projecting the boundaries of the inclusion onto the boundary between the two other phases. This reduces the 3D problem to one on a 2D surface while still being embedded in 3D space, which significantly reduces computational expense of solving the system. The resulting model is similar to conventional phase-field models. The properties of the solution are examined, compared to classical theory, and the numerical behaviour, including a mesh sensitivity analysis, are discussed. The model accurately captures mesoscale effects, such as the Gibbs-Thompson effect, coarsening, and coalescence. An example application of the model simulating the evolution of grain boundary porosity in nuclear fuel is shown on a representative tetrakaidecahedron-shaped fuel grain.Graphical Abstract