Fatigue Crack Propagation in Transformation‐Toughened Zirconia Ceramic

Fatigue crack propagation under tension‐tension loading is observed in a transformation‐toughened partially stabilized zirconia (PSZ) ceramic containing 9 mol% MgO. Such subcritical crack growth behavior is demonstrated to be cyclically induced, based on a comparison with behavior under sustained loading (at the maximum load in the fatigue cycle) and at varying cyclic frequencies. Crack extension rates, which are measured as a function of the cyclic stress intensity range ΔK over the range 10^‐10 to 10^‐6 m/cycle, are found to be load ratio dependent and to show evidence of fatigue crack closure, similar to behavior in metals. Cyclic crack growth rates are observed at ΔK levels as low as 3 MPa°m^1/2 and are typically many orders of magnitude faster than reported data on environmentally assisted, subcritical crack growth in PSZ under sustained‐load conditions.