Development of anisotropic microstructure in uniaxially pressed alumina compacts

Alumina compacts are prepared by uniaxial pressing followed by cold isostatic pressing (CIP). Anisotropic microstructures of the compacts and their sintered bodies are reported. Anisotropic grain growth with sintering time was systematically examined through direct measurement of grain dimensions on SEM micrographs in various conditions. Experimental results indicated that average grain size was always larger in the plane parallel to the direction of uniaxial pressing, than in its perpendicular plane, for all sintering conditions. The difference in the average grain size increased in these planes with sintering time. The grain growth followed the cubic law and the rate constants were 4.8×10−21 and 1.9×10−21(m3/s), for the former and the latter, respectively, in specimen uniaxial pressed at 100 MPa and CIPed at 100 MPa. Many intra-granule fractures were observed in the compact in the plane perpendicular the pressing direction comparing with its parallel plane.