Densification mechanism maps for hot isostatic pressing (HIP) of unequal sized particles

Abstract

A model is developed for the mechanisms of densification of powder compacts of unequal sized powder particles subjected to isostatic pressures at elevated temperature. The regimes of deformation mechanisms examined are those of athermal plastic flow and power law creep. Specifically, a bimodal distribution of particle sizes is assumed and the model evaluates the magnitude of the interparticle contact areas and the interparticle contact stresses are for each type of particle. It is found that the smaller particles bear the burden of higher interparticle contact stresses and plastic strains on an average and, accordingly, there is no longer a single boundary on a densification mechanism map between the regions of athermal plastic flow and power law creep for the bimodal case but rather a separate boundary for each particle size. The results are discussed with respect to a previous densification model for monosized particles, and the implications for a full size distribution are analyzed based on the bimodal results.