Particulate scale MPFEM modeling on compaction of Fe and Al composite powders

Abstract

In this paper, 2D single action die compaction of Fe and Al composite powders was simulated by multi-particle finite element method (MPFEM) from particulate scale. The initial packing structure generated by discrete element method (DEM) was input into FEM model where the mesh division of each particle was discretized. The effects of Al powder content on relative density and distribution, stress and distribution, particle deformation, void filling behavior, and force transmission in the compact during compaction, pressure holding and pressure releasing were systematically studied and analyzed. The results indicate that with the increase of Al content, high relative density can be obtained under the same compaction pressure, and the force chain structure becomes loose. When the Al content is fixed, the force is mainly concentrated on the Fe particles forming the contact force network which impedes the compaction densification. During compaction, void is mainly filled by the deformation of adjacent Al particles. It is difficult to deform those Al particles underneath the bridge or arching structure of Fe particles. Therefore, some small enclosed pores still left in the final compact. The internal stress in a particle is mainly concentrated near the surface region, and decreases rapidly after pressure releasing, while some residual stresses still exist inside Fe particles, leading to the possibility of cracking in the compact after unloading. Normally, the larger the compaction pressure is, the higher is the average residual stresses in Fe particles after releasing, and the largest local residual stresses occur in Fe particles close to the upper punch and die wall.