Evaluation of the Mechanical Properties and Fatigue Resistance of the ZrO2CeYAl2O3 Composite

This work aimed to evaluate the fatigue limit of the zirconia ceramic composite stabilized with yttria and ceria reinforced with alumina platelets (ZrO2CeYAl2O3) and characterize the mechanical properties of sintered specimens. Bar-shaped specimens were compacted by uniaxial pressing in a rigid die and sintered at 1500 °C-2 h. Subsequent characterizations included quantitative phase analysis by X-ray diffractometry, determination of density, modulus of elasticity, microhardness, fracture toughness, four-point flexural strength, and fatigue limit. Observations of fracture mechanisms were carried out using confocal and scanning electron microscopy (SEM). The sintered samples presented values above 98% of relative density. Complex microstructures with equiaxed, homogeneously distributed submicrometer grains and planar alumina platelets were observed by SEM. The composite samples showed high values of fracture toughness due to the transformation, during the test, from the tetragonal to monoclinic phase, causing an increase in volume and creating compression zones around the crack, making it difficult to propagate. The average flexural strength reached 445.55 MPa, with a Weibull modulus (m = 16.8), revealing low flexural rupture stress data dispersion. In the composite evaluated in this work, the occurrence of the tetragonal → monoclinic transformation that occurs in the Ce-TZP present at the triple points and grain boundaries during cyclic loading produces “crack tip shielding”, that is, a restricted elastic zone (zone shielding) that surrounds the crack tip. This phenomenon leads to a reduction in the stress intensity factor at the tip of the crack and slows down its growth, generating an increase in the fatigue resistance of the composite.