CONSTITUTIVE MODELS FOR THE SINTERING OF CERAMIC COMPONENTS .2. SINTERING OF INHOMOGENEOUS BODIES

A sintering model recently developed by the authors to predict grain growth, densification and creep deformation during sintering is used to analyse the response of a sintering body containing a distribution of spherical and ellipsoidal inclusions The analysis was performed using the finite element code ABAQUS, in which the grain size and relative density are considered as solution dependent state variables. The development of microstructure and residual stress field within the body are described in detail. For a prolate (fibre-like) inclusion a zone of high compressive mean stress develops around the tip of the inclusion, where densification and grain-growth occur at an accelerated rate. Eventually, because of the high density and large grain size the material within this zone becomes highly creep resistant and effectively forms an extension to the original inclusion. During the early stages of sintering the maximum principal stress, achieves its maximum value in the matrix at the interface with the inclusion, but away from the tip. As sintering progresses the peak moves away from the interface to the edge of the creep resistant zone, i.e. to the surface of the "effective inclusion". Similar results are obtained for an oblate (disc-like) inclusion, except that the general levels of stress are lower.