EFFECT OF THE GRANULE PROPERTIES AND COMPACTION PRESSURE ON THE GREENAND SINTERED DENSITIES OF AL2O3 15 VOL-PERCENT-ZRO2

The dependence of green and sintered densities of zirconia-toughened a lumina (ZTA:Al2O3/15 vol% ZrO2) on the properties of spray-dried granu les and compaction pressures was studied to differentiate the dominant processing parameter controlling sintered properties. Two sets of spr ay-dried granules, which differed largely in terms of the morphology a nd yield stress of granules, were compacted at various uniaxial pressu res in the range of 80 MPa to 120 MPa. The green and sintered densitie s varied depending on the granule properties and compaction pressure. However, both sets of granules formed by cold isostatic pressing at 50 0 MPa exhibited the same green and sintered densities of about 63% and 99%, respectively, relative to the theoretical density, regardless of the variation of granule properties. This work, confirmed that high c old isostatic pressure could overcome the effect of granule properties on the green and sintered densities. The strength of sintered specime ns was determined from the size of large hollows in the spray-dried gr anules remaining after compaction. Details of the compaction behavior in terms of the granule properties were discussed.