Environmental effects on the room-temperature static fatigue behavior of polycrystalline mullite

The room-temperature static fatigue behavior of a sintered polycrystalline mullite was studied in water and alkaline solutions, respectively. It was found that there exists a characteristic stress above and below which the delayed failure of mullite in liquid media may be controlled by different mechanisms. The conventional single-worst-crack model was employed to explain the time-dependence of the delayed failure of mullite in higher stress range while a microstructural damaging process was considered to dominate the failure in lower stress range. The possible molecular reactions between surrounding medium and mullite at the crack-tip were also discussed briefly.