Phase-field study of pore-grain boundary interaction

During final stage sintering, a complex interplay of densification and grain growth dominates microstructural evolution. Grain growth starts, when pore drag effects become less important due to pore shrinkage. This grain growth then decreases the driving force available for sintering. Accordingly, the interplay of pores and grain boundaries needs to be considered in detail. A phasefield model was extended to treat pore dynamics under consideration of pressure stability. To study pore attachment and detachment at moving interfaces, an idealized hexagonal microstructure with a constant driving force relationship for pore migration is constructed. Additionally, realistic polycrystalline microstructures were used. The model is in good agreement with experiments and analytic equations. Three different cases were observed in the realistic microstructure: pore attachment at the moving interface, partial and total pore detachment. However, in the partial case, the initial location of pores was found to be important: pores tend to migrate from quadruple junctions over triple junctions to grain boundary planes, where they eventually detach. This results in a variation of pore detachment, which is not captured in analytic equations. ... mehrTherefore large simulation setups are required to reflect the impact of initial pore location on pore drag effects.