Mechanical properties and microstructures of co-precipitation derived tetragonal Y2O3-ZrO2-Al2O3 composites

Y-TZP Al₂O₃ specimens (2.5 mol% Y₂O₃-ZrO₂ and 5 to 30 wt% Al₂ 03) were prepared from coprecipitated powders and their mechanical properties were studied. The addition of alumina to Y-TZP improves the attainable density of the materials after sintering at 1500° C and reduces the degradation of their densities due to porosity formation when the materials are sintered above 1500° C. Near theoretical density could be achieved for most of the samples after HIPing at 1500° C for 1/2 h at 200 M Pa pressure. The fracture strength of the HIPed specimens was in the range 2.0 to 2.4 GPa and the stress intensity factor was in the range 3.5 to 6.0 MPa m^1/2. The mechanical strength of the materials was not degraded seriously after autoclaving in water at 175° C for 24 h. The surface layer of transformed monoclinic zirconia was less than 70 m thick even after autoclaving at 175° C for 5 days.