Processing contributions to microcrack formation in ZTA composites. [Zirconia-Toughened Alumina]

Zirconia/alumina composites, in which the 3Y-PSZ content was varied between 5 and 30 vol pct, were prepared from dense (50 vot pct solids) aqueous suspensions by colloidal filtration. A systematic SEM study of the dispersion of particles showed that zirconia provoked the flocculation of powder mixtures. The extent of heteroflocculation appeared to depend upon the amount of zirconia added, and correlated with the properties of dense suspensions (electrophoretic mobility, viscosity, casting constant) as well as with the microstructure and mechanical properties of consolidated bodies. SEM observation of fracture surfaces of green samples revealed the presence of cracklike voids separating the grain clusters. When cast samples were isostatically pressed, a step which should serve to remove the cracklike defects, their mechanical properties changed significantly. 51 refs.