抄録
Zirconia based fine ceramics have a mechanism to improve the strength and the fracture toughness due to the stress induced phase transformation(the t-m phase transformation). They are expected to be used as a candidate material of the high heat resistant structures with complex shapes such as the core barrel and the upper shield block in the high-temperature gas cooled reactor. However, detailed data of the fatigue characteristics of zirconia based fine ceramics aren't sufficient yet. In this study, fatigue strength properties of 3mol% yttrium-stabilized tetragonal zirconia polycrystals (3Y-TZP) are estimated by fatigue test of 4-point bending at high temperatures. The changing of the crystal structure of 3Y-TZP due to the fatigue phenomenon are also evaluated by the X-ray diffraction analysis. In the fatigue test, the fatigue limit of the 3Y-TZP is about 500[MPa] and about 300 [MPa] under a condition of a ratio of the minimum and the maximum stresses of 0.1 at 523 [K] and 773[K], respectively. And the phase transformation determines the fatigue strength.
