Determination of pore mobility during sintering

The mobility of pores being dragged by grain boundaries has been modeled in terms of shape-independent microstructural parameters measurable by stereological means. The derived mobility is expressed with respect to the amount of porosity per unit area of grain boundary and the driving pressure for grain boundary and pore motion,i.e., as velocity per unit driving pressure. The resultant mobility for pore surface diffusion-controlled motion is found to be inversely proportional to the mean-pore intercept, regardless of pore shape and volume fraction. Solutions for lattice and vapor transport yield mobilities independent of pore size but inversely proportional to pore volume fraction. Computed pore mobilities, assuming surface diffusion-controlled motion, during final-stage sintering of copper and tungsten are shown to decrease with densification. In one case, mobility was found to increase during early densification, prior to the final stage. These results are explained with reference to the simultaneous changes occurring in grain boundary and pore surface areas during densification.