Plasticity‐Induced Fatigue Damage in Ceria‐Stabilized Tetragonal Zirconia Polycrystals

Abstract

Current studies on the fatigue lifetime of ceramics are mostly focused on the relation between the stress amplitude (or maximum Stress) and cycles to failure. For a more compliant and plastic ceramic which has a pronounced nonlinear stress–strain relation, the role of plastic strain in the fatigue damage is investigated for the first time in this study using a 12 mol% Ce‐TZP. By testing at different temperatures, we were able to vary the amount of transformation plasticity with the same microstructure. The Coffin–Manson relationship, which suggests that fatigue lifetime in the low cycle fatigue regime is best correlated with the plastic strain range, was confirmed for the tough ceramic. Fatigue damage is found to be a bulk process which continuously degrades flaw tolerance by microcracking. Evidence for the latter mechanism was also provided by uniaxial cyclic tension–compression stress–strain response and by TEM examination. Despite such damage, the possibility of plasticity‐induced surface‐crack nucleation in fatiguing ceramics, unlike in metals, appears unimportant.