MPFEM simulation of compaction densification behavior of Fe-Al composite powders with different size ratios

Abstract

In this paper, 2D single-action die compaction process of Fe-Al composite powders with different size ratios was simulated via the multi-particle finite element method (MPFEM) from particulate scale. Different initial packing structures generated by discrete element method (DEM) were imported into FEM model (where each particle was discretized for mesh division) for compaction. The compaction process was reproduced and the densification dynamics and mechanisms were analyzed and identified based on the evolution of macro and micro properties of the compact. The results indicate that, when the Al contents in the composite powder and the compaction pressure are fixed, higher relative densities can be obtained at smaller Fe/Al size ratios. During compaction, large stresses are mainly concentrated within those contacted Fe particles (near the surface region), forming the contact force network which impedes the compaction densification. Upon unloading, the contact force network is broken, and most internal stresses are released while only small amount of residual stresses are remained within Fe particles, which is susceptible to cracking or even failure during further processing. The smaller the Fe/Al size ratio is, the more complete is the release of the residual stress. During compaction, large voids (or pores) formed in the initial packing are filled by particle rearrangement (especially the rearrangement of small Fe particles) and plastic deformation of Al particles. However, there are still some small enclosed pores left in the final compact, which will lead to non-uniform deformation of adjacent particles and stress concentration during the subsequent sintering process.