Uniaxially Cold Compacted Green Parts: Shrinkage Kinetic Law and Effective Particle Size

摘要

In a previous work, a shrinkage kinetic equation was derived from a physical model accounting for the geometrical condition of the powder particles in prior cold compacted green parts. Among the material parameters affecting shrinkage, the particle size has a large effect, as well known. But commercial powders have a broad particle size distribution and the median value is often used. The equation has been experimentally verified by means of dilatometry tests on uniaxially cold compacted iron specimens, observing a discrepancy between the theoretical and the experimental shrinkage. Since all the other material parameters can be quite precisely defined, the difference was attributed to the incorrect definition of the particle size. The match between the theoretical and the experimental shrinkage was therefore obtained by introducing an effective particle size and the validity of this approach was verified on specimens with different density and orientation with respect to the compaction direction.