Resistance against crack nucleation and propagation in Y2O3 doped tetragonal zirconia ceramics

Both the nucleation and the propagation behavior of cracks have been investigated in Y-TZP ceramics, focusing on the effect of anelasticity. Indentation testing was carried out under the conditions of various loading speeds (40 and 300 μm s−1) and temperatures (198–367 K). A high resistance against cracking was observed at the lowest loading speed at higher temperature, which indicates that an activated anelasticity could release the stress concentration, resisting crack nucleation. As for the crack propagation behavior, the variation of the stress intensity factor, K, during the monotonic loading process was investigated using indentation pre-cracked sample. The effect of stress rate (8×10−4, 8×10−1 and 8×102 MPa s−1) and temperature (RT and 373 K) are reported. Extreme crack growth suppression was observed at lower stress rate at higher temperature. Under this condition, a strong resistance against the commencement of crack propagation was especially enhanced by activated anelasticity, resulting in an extended increase in K with increasing applied stress. These results suggest that the anelasticity could work as favorable effect on crack nucleation and propagation. However, it was found that exhaustion of anelasticity could cause a decrease in the fracture toughness.