Fatigue Deformation Mechanisms of Zirconia Ceramics

Two distinct fatigue deformation mechanisms, microcracking and transformation plasticity, have been identified in 3Y‐TZP and Mg‐PSZ. Microcracking is dominant in 3Y‐TZP, while transformation plasticity is more evident in Mg‐PSZ. However, the proportion of these two mechanisms is dependent on the frequency and stress amplitude, with transformation plasticity favored at low frequency and high stress. Generally, microcracks form in the tensile half‐cycle and partly close in the compressive half‐cycle, whereas transformation from the tetragonal to the monoclinic phase, as well as the reverse transformation, can occur in both tension and compression. Under stress‐controlled cycling, although the initial hysteresis loop is highly asymmetric with respect to the stress, cyclic softening and the development of an internal stress cause it to gradually evolve to yield an essentially symmetric cyclic stress–strain curve.