Indentation fatigue in random and textured alumina composites

The effect of grain orientation on contact fatigue behavior has been investigated by using alumina with elongated grains as a model system. Two kinds of composite microstructures, textured and random, mere prepared by controlling the processing conditions. The textured material has the platelets aligned parallel to the surface, and the random material has the platelets randomly oriented, The Hertzian indentation results show that, although both materials exhibit damage accumulation with increasing number of cycles due to frictional degradation at the microstructural level, the damage evolution rate is much lower for the textured material, This suppression of fatigue damage in the textured material appears to result from the lower shear stress concentration along the textured weak interfaces between elongated alumina grains. The implication of the present results for structural design in improvement of contact-fatigue resistance is also addressed.