A stereological model of the degree of Grain Boundary-Pore Contact during Sintering

Abstract

A simple geometric model of pore and grain structure has been used to explain the experimentally observed constancy of the degree of grain boundary-pore contact,R, throughout intermediate and final stage sintering. As modeled, constancy ofR in the final stage requires a balance among the number of pores per grain, the ratio of the pore and grain sizes, and the relative frequencies of pore locations at grain corners, edges, and surfaces. Experimentally, these location frequen- cies were found to remain constant for both pure and MgO-doped A12O3, over the observed range from 91 to 99.8 pct of full density. The number of pores per grain increased and the pore/grain size ratio decreased over this period for both materials. Employing experimental microstructural data for the above parameters in the model yielded the predicted linear plots, with intercepts givingR values very close to the values measured by direct stereological means. The model also yielded reasonable, constant values ofR for intermediate stage sintering and explains the constancy ofR throughout the transition from intermediate to final stage.