GREEN PM COMPACTS INCORPORATING INTERNAL STRUCTURES

A novel method of producing die-compacted powder metallurgy (PM) components with a fully enclosed, stearic acid-filled internal structure (IS) was developed. The physical characteristics and strength of the compacts were evaluated by measuring bulk density, internal density gradients, and compressive green strength. Additionally, a finite element (FE) simulation was developed to evaluate the compaction process of the IS. The IS compacts displayed the anticipated reduction in bulk density compared with a conventional PM compact due to the lower density of the IS. Higher local densities were found within the IS compacts at all compaction pressures. Compressive green strength increased with compaction pressures up to 300 MPa but at a compaction pressure of 400 MPa there was a plateau in green strength. This phenomenon is attributed to an increase in the differential shear stress around the IS with minimal increase in density for compaction pressures from 300 MPa to 400 MPa.