Fracture behaviour of an Al2O3-ZrO2 multi-layered ceramic with residual stresses due to phase transformations

摘要

The fracture behaviour of a ceramic multi-layer designed with thin internal compressive layers and obtained by slip casting is studied. It consists of nine alternated Al2O3-5vol%tZrO(2) and Al2O3-30vol%mZrO(2) layers of 530 mu m and 100 mu m thickness, respectively. Mechanical characterization includes evaluation of Vickers Hardness, Young's modulus and fracture strength under four-point bending. In addition, the residual stress magnitude and distribution in the laminate is determined both analytically, from calculations using the differential strain between layers and the elastic properties, and experimentally, using indentation techniques. The experimental findings in terms of mechanical strength and fractography show a subcritical growth of the natural flaws in the laminate before catastrophic failure occurs, owing to the relevant role of the thin Al2O3-30vol%mZrO(2) layers with compressive stresses inherent to the zirconia phase transformation. These layers are also responsible for the increase in toughness to levels of at least three times that of the reference Al2O3-5vol%tZrO(2) monolith.