GRAIN-SIZE DEPENDENCE OF HARDNESS IN DENSE SUBMICROMETER ALUMINA

Pressureless sintered alumina compacts with a submicrometer microstruc ture exhibit a hardness that approaches or even exceeds the level of a dvanced hot-pressed composites of Al2O3 + 35 vol% TiC, whereas the str ength of both ceramics is approximately the same, The combination of r educed dislocation mobility (due to the small grain size), high densit y, and density homogeneity are the prerequisites for the surprisingly high hardness. Quasi-conventional powder processing is used to produce these outstanding alumina bodies.