MECHANICAL-PROPERTIES OF HOT ISOSTATICALLY PRESSED ZIRCONIA-TOUGHENED ALUMINA CERAMICS PREPARED FROM COPRECIPITATED POWDERS

Amorphous Al2O3-ZrO2 Composite powders with 5-30 mol% ZrO2 have been prepared by adding aqueous ammonia to the mixed solution of aqueous aluminum sulfate and zirconium alkoxide containing 2-propanol. Simultaneous crystallization of gamma-Al2O3 and t-ZrO2 occurs at 870-degrees-980-degrees-C. The gamma-Al2O3 transforms to alpha-Al2O3 at 1160-degrees-1220-degrees-C. Hot isostatic pressing has been performed for 1 h at 1400-degrees-C under 1% MPa using alpha-Al2O3-t-ZrO2 composite powders. Dense ZrO2-toughened Al2O3 (ZTA) ceramics with homogeneous-dispersed ZrO2 particles show excellent mechanical properties. The toughening mechanism is discussed. The microstructures and t/m ratios of ZTA are examined, with emphasis on the relation between strength and fracture toughness.