Elevated temperature mechanical properties of partially sintered alumina

The influence of porosity on the mechanical response of alumina prepared by the partial sintering of micron-sized powders has been evaluated at room temperature and 1100 °C using 4-point flexure and compression creep tests. An approximate fivefold increase in both flexure strength and modulus was observed with an increase in sample density from 55% to 70%. The significant reductions in steady-state creep rates measured for a constant applied stress was also quantified as a function of increasing density. Electron microscopy showed a rapid increase in the degree of interparticle contact and bonding following limited densification. The increases in flexure strength and modulus were well described by currently available analytical relationships. Compression creep rates could be predicted by a model developed for the densification of porous materials through diffusional creep.