Modelling of three powder compaction laws for cold die pressing

Three models to describe the relationship between the green porosity of compacts and the applied external pressure during the compaction of metal powders are proposed in order of growing complexity. Only in the third model do all of the parameters have a clear physical meaning and become measurable. These parameters are related to the plastic behaviour of the powder particle material, the friction coefficient between the powder and die walls, as well as the interparticle friction. The three proposed models include a parameter representing a certain value related to the initial porosity of the powder mass; however, only in the third model is this value clearly defined by the tap porosity of the powders. The proposed models have been experimentally verified by compressibility curves obtained from metal powders of different types. The agreements between the second and third models and the experimental data are reasonable over the tested pressure range.