STRESS RATE DEPENDENCE OF FRACTURE STRENGTH IN PRECRACKED ZIRCONIA CERAMICS

In this study, the fracture strength of three kinds of zirconia cerami cs, 2Y-TZP, 8Y-FSZ and 9Mg-PSZ is investigated under vast range of str ess rate (10(-3) - 10(3) MPa s(-1)) by using indented rectangular samp les. Compared with other ceramics like silicon nitride, the fracture s trength of zirconia ceramics is found to be affected more by the envir onment, which causes a slow (or subcritical) crack growth (SCG) behavi or. However, the strength degradation by SCG can be saved to some exte nt for 9Mg-PSZ and 2Y-TZP by the phase transformation triggered by the environmental factors like H2O and O-2, or the well-known stress indu ced phase transformation. Furthermore, in TZP ceramics, benefiting fro m its specific anelastic behavior possibly caused by ferroelastic doma in switching or grain reorientation, the fracture strength is greatly improved in lower stress rate region at 523 K, though a strength degra dation at this temperature was stated in many past literatures. (C) 19 98 Elsevier Science S.A. All rights reserved.