In Situ Analysis of the Powder Behaviour during Cold Compaction

Cold compaction experiments were carried out on stainless steel powders, using a 200 tons hydraulic press. The force and the displacement of the axes were recorded and a force-displacement curve was determined. Green parts with different H/D ratio and different green density were produced. The measured displacement is due to the contribution of the following phenomena: powder rearrangement, elastic and plastic deformation of the powder, elastic deformation of the tools (punches, bearings and the plate supporting the die). Rearrangement and plastic deformation of the powder are irreversible. The contribution of the reversible phenomena (elastic deformation of powder and tools) and of the irreversible phenomena (rearrangement and plastic deformation) was investigated analysing the loading and unloading curves of the compaction cycle at different maximum forces.