Fatigue Behavior of Tetragonal Zirconia Polycrystals Containing 4mol% Y2O3

Fracture stress (σf) of tetragonal zirconia ceramics containing 4mol% Y2O3 was measured as a function of stressing rate (σ) (dynamic fatigue). Linear relationships were obtained between log σf and logσ at room temperature. Crack growth parameters N obtained from the slopes of the linear relationships were 32 for grain size of 0.47μm (Z4Y-Ia), 33 for 0.62μm (Z4Y-Ic) and 46 for 1.34μm (Z4Y-II). A linear relationship was observed between log σf and log σ for Z4Y-Ic at 250°C, and the N value was 41. Log σf for Z4Y-II at 250°C was constant at stressing rates above 30.2MPa/s. The N value obtained for stressing rates below 3.02MPa/s was 8.7. The time to failure tf under several applied stresses σ's measured for the specimen with a grain size of 1.34μm (Z4Y-II) at 250°C (static fatigue) was similar to the life time predicted from dynamic fatigue data. A linear relationship was observed between logtf and logσ, and the N value obtained from the slope was 7.3.