INFLUENCE OF SLIP-CASTING AND DRY-PRESSING ON STRUCTURE EVOLUTION OF ALUMINA COMPACTS

A commercial alumina powder was processed to remove aggregates and agglomerates for the study of processing influence on sintering behaviour and structure evolution. Slip-casting a uniformly dispersed slurry formed green compacts with homogeneous particle packing, which subsequently resulted in a nearly defect free microstructure upon sintering. Dry-pressing the granules that possessed a similar homogeneous microstructure led to compacts with larger voids and particle-packing inhomogeneity. The inhomogeneity persisted through sintering and evolved voids with a size of about 6 mum. However, under the same sintering condition, the sintered density of the dry-pressed compact approached that of the slip-cast compact. The grain sizes of both sintered compacts were similar, implying that differences in consolidation effectiveness do not necessarily incur variation in grain growth provided the compacts are prepared from the same starting powder and sintered under the same condition.