Coupling the discrete element method and solid state diffusion equations for modeling of metallic powders sintering

Abstract

A novel discrete element method-based approach for modeling of solid state sintering of spherical metallic powder is presented. It tackles the interplay between the thermodynamical mass transport effects arising in the vicinity of the grain boundary between the particles and their mechanical interaction. To deal with the former, an elementary model is used that describes the behavior of the matter flow at the grain boundary such that neck growth and shrinkage are properly captured. The model solves a set of partial differential equations which drive the changes of the corresponding geometry parameters. Their evolution is transformed into the equivalent normal sintering force arising in each sinter neck. To capture the mechanical interaction of particles due to their rearrangement resulting from the geometry changes of each individual contact, the entire assembly is modeled as an assembly of 2-nodal structural elements with 6 degrees of freedom per node. The stiffness properties are estimated employing the approximations from the bonded DEM. The numerical implementation then constitutes a two-step staggered solution scheme, where these models are applied sequentially. The performed benchmarks reveal the plausibility of the proposed approach and exhibit good agreement of both neck growth and shrinkage rates obtained in the numerical simulations with the experimental data.