Sintering models and the development of instabilities

Abstract

A mathematical model is developed to describe, at least approximately, the densification and reorganization of a random stacking of particles due to internal transport of material. In this model, local stresses due to time varying coordination of particles are allowed which are found to alter the overall sintering behaviour significantly. Further, variations on stacking density and coordination on both a local and a global scale are investigated for their influence on small and large scale particle reorganization during sintering. It is found that these local variations will easily give rise to the development of a porosity of high coordination along with local densification. The overall effect is that this porosity disappears after a large sintering period when grain growth has become already substantial.

Global variations in coordination are seen to be responsible for defect formation. A number of criteria will be derived to estimate under which conditions this formation of defects may be expected. The present model will be discussed with the help of own and a number of examples found in the literature.