Neutron diffraction residual stress analysis of zirconia toughened alumina (ZTA) composites

Measurements of the residual stresses in zirconia toughened alumina (ZTA) composites, containing 1.7, 14 and 22 vol% yttria-stabilized zirconia (3Y–TZP) were obtained by neutron diffraction. Over the range of volume fraction investigated, the hydrostatic stress in alumina and zirconia phases varies roughly linearly with the zirconia content. It is shown that these features can be qualitatively understood by taking into consideration the thermal expansion mismatch between the ZrO2 and Al2O3 grains. In addition, a decrease of the Al2O3 line broadening is observed, which implies a decreasing micro-residual strain due to the ZrO2 particles in the alumina. It is inferred that the residual strain field is highly hydrostatic, and that a decrease of the grain boundary shear stress occurs as a function of the reinforcement volume fraction. This phenomenon is more important in the case of 1.7 vol% zirconia composite because the zirconia particles are in the nanometre size range, with a narrow distribution.