Comparison of Slow Crack Growth Behavior in Alumina and SiC-Whisker-Reinforced Alumina

Results of dynamic fatigue experiments in water at room temperature on an indented Al₂O₃/25 wt% SiC whisker composite material have shown that this composite has a high resistance to slow crack growth. Aging tests in water revealed that the residual stress due to the indentation does not play an important role, and interrupted fatigue tests showed that the crack starts to grow at very low stress intensities, but the velocity is very low. Detailed fractography indicated that the slow crack growth path is intergranular in the whisker composite. The slow crack growth behavior in the whisker composite is discussed in association with the indentation residual stress, the change of the crack shape during the bending test. These results are compared with a bio-grade Al₂O₃ with lower resistance to slow crack growth, and important differences are pointed out.