Geometric model of sintering of unequal-sized particles

Abstract

Sintering is a materials processing method generally applied to high-melting point materials. Performance of a sintered product is influenced by its microstructure. The effects of processing parameters, such as sintering time and temperature, on the microstructure are usually understood with the help of geometric models. Most geometric models assume equal-sized particles in the powders. This assumption neglects coarsening by inter-particle mass transport and grain boundary migration. Moreover, this assumption is seldom true in practice; because, coarsening and grain boundary migration always occur during sintering, especially during sintering of nanosized and ultrafine particles. In this paper, we present a model to quantitatively describe the sintering process of powders with unequal-sized particles. The present model relies on calculations of diffusional flux for neck growth and coarsening during sintering. In addition, we derive an expression to describe the grain boundary migration. We apply the model to predict the sintering behaviour of two equal-sized particles, two unequal-sized particles and a row of unequal-sized particles. We validate the model by comparing with Kingery and Berg's model, phase field simulations, and sintering experiments. The comparison showed that the model can be used to predict the sintering process with a reasonable accuracy.

Keywords:

• sintering
• theory and modelling
• neck growth
• coarsening
• grain boundary migration