Deformation structure and magnetic properties of iron powder core compacted at high pressure

Abstract

This study investigates how compaction pressure and die shape influence the density distribution and related magnetic and electrical properties of pure iron based green compacts. By combining empirical densification models with geometry-specific corrections for wall friction and shear deformation, numerical simulations were conducted for three die types: cylindrical, prismatic, and ring. The simulations predict spatial variations in densification that align with experimental observations from optical microscopy. Results show that high compaction pressures (up to 2500 MPa) can enhance magnetic performance by increasing density and reducing porosity, but they also cause significant inhomogeneities, especially in cylindrical shapes, due to stress localisation near die walls. Ring-shaped compacts demonstrate better uniformity in both density and magnetic properties, confirming the importance of geometry-dependent modelling of compaction. Surface flash formation and grain deformation at the die–punch interface align with shear-enhanced densification zones forecasted by the model. Overall, the findings emphasise the need to consider both friction and shear effects when designing powder metallurgy processes for soft magnetic materials.