Effect of the Crystal Grain Size on the Cyclic Fatigue Behavior of Glass Ceramics. (Examination for Multiple Surface Cracks in Water Environment).

Abstract

In order to examine the effect of crystal grain size on the fatigue behavior of glass ceramics, cyclic fatigue tests were carried out by four-point bending load under both environments in air and water. A single crack and three collinear cracks were introduced on the surface of plate specimens by Vickers micro hardness indentation. The crystal grain size of the glass ceramics in this work was about 1μm, and it was increased from about 0.05μm used in previous work. As a result, the time-to-failure to the cyclic fatigue of the glass ceramics with a large crystal grain size obviously did not decrease by the effects of water environment and the multiple surface cracks, comparing with that of the glass ceramics with a small crystal grain size. Therefore, the interaction between multiple surface cracks may not be effective sufficiently for glass ceramics with a large crystal grain size. In addition, the fatigue strength of the glass ceramics increased with increasing crystal grain size. These facts mean that a dominant crack propagates along crystal grain boundaries.