SINTER-Plus-HIPING OF ZIRCONIA AND ZIRCONIA-TOUGIENED ALUMINA (ZTA) CERAMIC MATRIX COMPOSITES

摘要

Yttria-tetragonal zirconia polycrystals (Y-TZP), and yttria-partially stabilized zirconia composites containing different weight percentages of aluminum oxide (Zirconia-Toughened Alumina (ZTA)) were successfully post-sintering hot-isostatically pressed (Sinter-plus-HIPed) to their theoretical density, i.e. > 99.5percent TD. Hiping has no measurable effects on hardness (H) and fracture toughness (KIc) properties, as they were determined using Vicker's micro-indentation technique. No phase changes in the crystallinity of these oxide ceramic composites, due to hiping, were observed. Low temperature annealing, i.e., < = 57 3 K, in a humid atmosphere has caused severe degradation of as-sintered, as well as, the sinter-plus-hiped Y-TZP ceramics. The alumina-containing Y-PSZ composites have shown an excellent resistance to low-temperature annealing. High-temperature annealing, i.e., 1573 K in air atmosphere, had insignificant effects on H and KIc of Y-TZP, while about 10percent decrease in the KIc value of Y-PSZ/alumina composites was observed due to the increase in the mole fraction of the cubic phase of zirconia with consistent decrease in the fraction of the tetragonal phase, as it has been determined by quantitative phase analyses using x-ray diffractometry.