Microstructure and high-temperature mechanical behavior of alumina/alumina-yttria-stabilized tetragonal zirconia multilayer composites

Layered composites of alternate layers of pure Al2O3 (thickness of 125 mu m) and 85 vol% Al2O3-15 vol% ZrO2 that was stabilized with 3 mol% Y2O3 (thickness of 400 mu m) were obtained by sequential slip casting and then fired at either 1550 degrees or 1700 degrees C, Constant-strain-rate tests were conducted on these materials in air at 1400 degrees C at an initial strain rate of 2 x 10(-5) s(-1). The load axis was applied both parallel and perpendicular to the layer interfaces. Catastrophic failure occurred for the composite that was fired at 1700 degrees C, because of the coalescence of cavities that had developed in grain boundaries of the Al2O3 layers. In comparison, the composite that was fired at 1550 degrees C demonstrated the ductility of the Al2O3+YTZP layer, but at a flow stress level that was determined by the Al2O3 layer.