Cyclic Fatigue of Yttria Tetragonal Zirconia Polycrystals

摘要

The use of advanced ceramic materials rather than metallic materials for structural applications, such as in gas-turbine engines, has been motivated by their low density, far superior elevated-temperature strength and presumed insensitivity to degradation from cyclic fatigue (1). Several recent reports, however, have given evidence for reduced lifetimes under cyclic loadings at stress levels clearly below the flexure strength. The report presents results from cyclic, monotonic and static loadings of test bars of yttria tetragonal zirconia polycrystals (Y-TZP). The tests were performed in 4-point bending at room temperature. The fractured surfaces of the samples were investigated by low-power optical microscopy and by high magnification scanning microscopy. Microhardness and fracture toughness were measured with the indentation technique. X-ray diffraction analysis was used to evaluate the crystallographic changes taking place during the mechanical tests.