Constitutive modelling of the densification of micron-grain-sized alumina ceramics

In the present work, the densification behaviour of micron-grain-sized alumina during stage 1 sintering is studied by the constitutive models employed and the experimental results obtained. Grain-boundary diffusion is identified as the dominant densification mechanism of the materials system investigated, and the corresponding model is examined as an appropriate form. The activation energy for densification is evaluated as 384 kJmol(-1), which provides strong support for the dominant densification mechanism investigation. The appropriate expressions for some important parameters, namely the sintering potential and dimensionless density functions, in the constitutive law are identified from those reported in the literature. The relationship between the sintering potential and the relative density is studied and the trend that the determined sintering potential increases with increase in the relative density is shown. The grain-boundary diffusion constitutive law is then used to study the process of sintering of a micron-grain-sized alumina tape on a rigid alumina substrate. As a result, the model provides a reasonably good prediction for the densification behaviour of the constrained-sintered tape. The tensile stress, induced by the constraint is estimated and it is shown that the stress increases as the relative density increases.