Design and fracture of layered Al2O3/TZ3Y composites produced by electrophoretic deposition

Alumina/yttria-stablized tetragonal zirconia (Al2O3/TZ3Y) multilayer compos ites 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 deg reesC) to experimentally define conditions for crack deflection and flaw to lerance. The compressive residual stress in the Al2O3 layers (sigma (r)) is a function of layer thickness (t). It was found that the parameter oft is an effective indicator of the fracture behavior, as predicted by strain ene rgy release calculations. With decreasing sigma (2)(r)t, the fracture follo wed a sequence from spontaneous delamination, multistage fracture with exte nsive crack deflection, to catastrophic failure with, and finally without, deflection steps. Decrease of sigma (r) with increasing test temperature ca uses changes in fracture behavior which correspond to the room-temperature transitions of o(r)(2)t.