A granular model of equiaxed mushy zones: Formation of a coherent solid and localization of feeding

The gradual transformation of a mushy zone during alloy solidification, from a continuous liquid film network to a fully coherent solid, has been simulated using a granular model. Based on a Voronoi tessellation of a random set of nucleation centres, solidification within each polyhedron is computed considering back-diffusion and coalescence. In the network of connected liquid films, a pressure drop calculation is performed assuming a Poiseuille flow in each channel, Kirchhoff’s conservation of flow at nodal points and flow losses compensating solidification shrinkage (KPL model). In addition to intergranular liquid pressure maps, the model shows the progressive formation of grain clusters, the localisation of the flow at very high solid fraction and thus natural transitions of the mushy zone.