EVOLUTION OF YOUNGS MODULUS, STRENGTH, AND MICROSTRUCTURE DURING LIQUID-PHASE SINTERING

This comparative study addresses the influence of microstructural evol ution on mechanical properties of porous alumina prepared by partial d ensification with and without addition of a glassy phase. The composit ion used for liquid-phase sintering is heated above and, in order to f reeze the starting defect distribution, below the glass transition poi nt. The ensuing densification rate is compared with measurements of th e temperature and time-dependent wetting angle. The strength of the al umina is correlated with microstructural characteristics, Young's modu lus, fracture toughness, and crack tip toughness as a function of poro sity, Linkage of the crack tip toughness to elastic modulus, in combin ation with fractography and a description of a linearly shrinking crit ical defect, yields a predictive capacity to determine strength of por ous ceramics.