Phase transformation induced fatigue of a Ce-TZP/Al₂O₃ composite

In this study, the stress–cycle number (S–N curve) of a composite consisting of ceria-stabilized zirconia (Ce-TZP) and alumina (Al₂O₃) was measured. First, the initial bending strength of the Ce-TZP/Al₂O₃ composite was determined using a four-point bending technique. Next, stress above 70% of the initial bending strength was applied on the composite for up to 1,000,000 cycles. Transformation bands were formed on the tensile surface in the first several cycles as the stress was higher than a critical value. The number and width of bands then changed marginally after their fomraiton. Fatigue failure occured at the band with the largest width, as a result of slow crack growth process. The transformation bands could be removed using a post-fatigue heating treatment. After removal of these bands, the strength was consequently enhanced.