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.