Effect of porosity on hardness of Al2O3-Y3Al5O12 ceramic composite

In this work, the effect of porosity on hardness of Al2O3-Y3Al5O12 (YAG) ceramic composites was investigated. Al2O3 powders containing 20 wt.% and 36.5 wt.% of Y2O3, were mixed, compacted by cold uniaxial pressing at different pressures ranging from 40 MPa to 100 MPa, and subsequently sintered at 1600 degrees C for 2 h. The sintered samples were characterized by X-ray diffraction, presenting alpha-Al2O3 and Y3Al5O12 as crystalline phases. Samples with relative densities ranging from 78 to 80% and 87 to 91% were obtained depending on the composition and the compaction pressure used. The hardness values obtained were between 1010-1080 HV and 370-470 HV, for mixes of Al2O3-Y2O3 having the composition levels of 20 wt% and 36.5 wt.%Y2O3, respectively. The hardness was examined using classic exponential rule with pre-exponential constants which simulate the effect of porosity on the hardness of the sintered samples. These pre-exponential constants were identified to be 4.0 and 6.5 for compositions containing 20 wt.% and 36.5 wt.% Y2O3, respectively. (C) 2014 Elsevier Ltd. All rights reserved.