Hot Isostatic Pressing of Ceramic Powder Compacts

摘要

The densification of aluminum oxide in hot isostatic pressing has been studied in detail. Methods for calculating maps of densification rate as function of temperature and applied pressure have been developed. A new mechanism, interface-reaction-controlled grain-boundary diffusion, has been found which describes the densification of high-purity, fine-grained (grain radius of 0.7 micrometers) aluminum oxide powder at temperatures up to 1423 K. Theoretical models have been developed for this mechanism for both the initial and final stages of densification. Standard geometries have been used for the models; the initial stage is described in terms of impinging spherical particles, and the final stage is described in terms of isolated pores. The theoretical model is found to describe the data for fractional densities up to at least 0.9, although it breaks down for higher densities. From theoretical studies of final stage, we find indications that the discrepancy between theory and experiment is due at least in part to neglect of the effects of a distribution of pore sizes.