Microcracking Contributions to the Toughness of ZrO_2-Based Ceramics

Analyses are presented to evaluate two microcrack toughening situations in \nZr_O2-based ceramics. The first analysis considers toughening due to stress-induced \nmicrocracking of residually strained monoclinic ZrO_2 particles. The second assesses \nmicrocracking that occurs as a consequence of the stress-induced tetragonal-monoclinic \ntransformation. Both toughening mechanisms are characterized by a \npermanent dilatational strain and a modulus reduction; however, only the latter may \nresult in a toughness enhancement or reduction. Conditions under which toughness \nenhancement and reduction are observed are established. The magnitudes of \ntoughening increases from transformation-toughening and microcrack-toughening \nare also compared.