Isostatic compaction of bimodal powder mixtures and composites

We study the effect of using a mixture of particles of two different sizes for the compaction of spherical metallic powders by discrete element method simulations (DEM). The study focuses on large size ratios (4 and 8) for which a wide range of volume fractions of large particles is investigated (from 0% to 80% volume). The bimodality of the powder is shown to affect all stages of powder compaction. The relative density of the powder when no significant load is applied (tap density) is a function of both the size ratio and the volume fraction of large particles. Furthermore, we show that bimodal compacts exhibit a stiffer response during isostatic plastic compaction compared to the monomodal case. The important practical application of a mixture of soft deformable particles (metallic) with hard particles (ceramic) is also studied. Following compaction, the unloading of the compact and the resulting tensile strength (green strength) are also shown to depend on the bimodality of the compact.