Interactions between aging resistance and fatigue resistance, a case study on a ZrO ₂ /Al ₂ O ₃ composite

Abstract Zirconia is susceptible to external humid and loads in the form of phase transformation. Since the phase change is accompanied with many internal stresses and defects, the strength of the zirconia might be suffered. In order to ensure a long‐term stability, both aging resistance and fatigue resistance of zirconia should be evaluated. However, these two resistances are usually measured by separate tests, assuming that the monoclinic (m) phase induced by aging and by external load does not interact. Findings from this study challenge that assumption due to that the m‐phase formed during aging can serve as nuclei for further growth during fatigue. A Ce–ZrO 2 /Al 2 O 3 composite, known for its excellent aging resistance, is used to demonstrate such interactions. Our experimental results indicate that the amount of the m‐phase is increased during fatigue if the specimen is aged beforehand. Apart from independent aging and fatigue tests, a post‐aging fatigue tests could provide indication on the long‐term stability of zirconia.