Grain-boundary sliding model of pore shrinkage in late intermediate sintering stage under hydrostatic pressure

A grain-boundary sliding model is developed to characterize the shrinkage behavior of pores in the intermediate stage of sintering under compressive hydrostatic pressure. From an analysis of the relative sliding between grains, the bulk viscosity, densification rate and the shrinkage rate of pores are predicted for a dense matrix polycrystal containing spherical pores. Comparison with a continuum model shows that whereas the densification behavior in the present discrete model approaches the prediction of the continuum model for large pores, the occurrence of grain-boundary sliding is limited and the deviation from the continuum model increases significantly for small pores. It is also shown that the grain-size dependence of the densification rate observed experimentally is consistent with the model prediction and verifies the validity of the present model in the intermediate sintering stage.