Critical stress map for ZrO2 tetragonal to monoclinic phase transformation in ZrO2-toughened glass-ceramics

Inspired by recent observation of compressive stress induced tetragonal to monoclinic (t-m) phase transformation in yttria-stabilized zirconia, we conduct a systematic study to investigate the critical stress map for ZrO2 transformation under various loading conditions. The results show that (1) uniaxial tensile and compressive loadings can trigger the transformation, but not hydrostatic tensile and compressive loadings; (2) shear and equal biaxial tensile loading are most favored to trigger the transformation. Additionally, simulation on a model ZrO2-containing SiO2-based glass-ceramic shows that the stress fields around the running crack front can help triggering ZrO2 phase transformation, and consequently change the stress in ZrO2 from tensile to compressive and deflect the crack propagation. The insights obtained from these simulations can help us better understand ZrO2 transformation toughening mechanism, and further leverage it to enhance the mechanical performance of materials in many real applications.