Homogeneity of isostatic pressure-assisted sintering of agglomerated powder

This article is dedicated to the modeling of the pressure-assisted sintering of agglomerated powders by the grain-boundary and the surface diffusion transport. Agglomerates are treated as volumes with dense particle packing. Kinetics of sintering during consolidation is estimated by a direct numerical analysis of the matter redistribution by diffusion around a single neck between identical spherical particles. Type of packing is introduced into the model through the definition of the packing angle and a special symmetry boundary condition for diffusion fluxes. The numerical analysis of sintering parameters for a single neck allows the evaluation of macroscopic viscosities of the material for different types of the particle packing and enables the estimation of the densification rate of agglomerates and non-agglomerated elements of powder compacts. Calculations show that, despite low initial density and low initial viscosity of a loose powder around agglomerates, isostatic pressing cannot provide a complete equalization of local densities in an agglomerated powder. In all considered cases, agglomerates have reached final density faster than elements with looser packing. (C) 2004 Elsevier Ltd. All rights reserved.