Role of Autocatalytic Transformation in Zone Shape and Toughening of Ceria–Tetragonal‐Zirconia–Alumina (Ce‐TZP/Al ₂ O ₃ ) Composites

Abstract

Stress–strain behaviors in three‐point bending, transformation zones in single‐edge‐notch‐bend specimens, and transformation toughening were studied in two types of Ce‐TZP/Al 2 O 3 composites. A commercial grade exhibited yield‐point behavior triggered by autocatalytic transformation and elongated zones. A new grade of Ce‐TZP/Al 2 O 3 composite showed monotonic stress–strain behavior and a zone shape close to theoretical prediction based on a shear–dilatation yield criterion. The effects of zone sizes and shapes on fracture toughness of the two ceramic composites are shown to be qualitatively consistent with the predictions of transformation‐zone shielding theories.