On the determination of the stress-free temperature for alumina-zirconia multilayer structures

Internal residual stresses can enhance the fracture resistance and mechanical reliability of layered ceramics. The magnitude of the stresses depends on the elastic and thermal properties of the layers and the typically assumed reference (stress-free) temperature, below which internal stresses develop. A novel combined experimental and numerical simulation approach has been developed to determine the reference temperature and experimentally proved in alumina-zirconia ceramic laminates. Dilatometric data of monolithic phases are input for the numerical simulation and experimental data on the laminate properties are used for the stress-free temperature determination. In contrast to typical assumptions, reference temperature very near the sintering temperature (i.e. approx. Tref≈1470 °C) was found, which should be considered for the estimation of internal (residual) stresses in alumina/zirconia-based layered ceramics.