Cyclic fatigue behaviour of eutectoid aged Mg-PSZ ceramics with processing flaws

The cyclic fatigue behaviour of Mg-PSZ in the asfired state and after eutectoid aging (1400°C for 2 and 16 h) were investigated in four-point bending tests. A large number of specimens with processing flaws were used to measure the initial strength distribution and the cyclic fatigue lifetime at a stress ratio R = 0·3. From these experimental data a modified 'stresstime-probability' (S-T-P) diagram can be constructed using a statistical approach. The residual strength of the survivor specimens, which is lower than their corresponding initial strength, has also been measured, confirming that pronounced cyclic fatigue damage does occur in these Mg-PSZ ceramics. The experimental results are discussed in terms of transformation toughening, microcracking and precipitate hardening mechanisms.