Design and Fracture of Layered Al 2 O 3 /TZ3Y Composites Produced by Electrophoretic Deposition

Alumina/yttria‐stablized tetragonal zirconia (Al 2 O 3 /TZ3Y) multilayer composites with strong interfaces and containing residual stresses were produced by electrophoretic deposition. As‐synthesized and Vickers‐indented samples with different layering designs have been tested in bending (up to 1300°C) to experimentally define conditions for crack deflection and flaw tolerance. The compressive residual stress in the Al 2 O 3 layers (ς r ) is a function of layer thickness ( t ). It was found that the parameter ς r 2 t is an effective indicator of the fracture behavior, as predicted by strain energy release calculations. With decreasing ς r 2 t , the fracture followed a sequence from spontaneous delamination, multistage fracture with extensive crack deflection, to catastrophic failure with, and finally without, deflection steps. Decrease of ς r with increasing test temperature causes changes in fracture behavior which correspond to the room‐temperature transitions of ς r 2 t .