Modelling of solid-phase sintering of hardmetal using a mesomechanics approach

Abstract

The mesomechanics approach presented in this paper aims at enhancing the understanding of, as well as providing a predicting capability for, the densification process in cemented carbides due to solid-phase sintering. The major mesostructural constituents are tungsten carbide (WC) particles and large pores, which are embedded in a contiguous cobolt (Co) matrix. A preprocessor code, which is based on Voronoi polygonization, was developed to generate the morphology with prescribed area fraction and size distribution of the constituents. In a continuum model, the ‘driving force’ that brings about the densification is the sintering stress, which is given a rational thermodynamic definition in the paper. This stress represents the boundary loading of a representative volume element (RVE) at free sintering, i.e. in the absence of macroscopic stresses. In such a volume element (or unit cell) the constituents WC and Co are assumed as viscoplastic non-porous solids. A generalized Bingham model (of Norton-type with hardening) seems to be sufficient to represent the creep properties, which are assumed to be of dislocation as well as of diffusion type. The temperature dependence of certain material parameters is discussed. Thermal expansion is accounted for. The developed algorithm was implemented in the commercial FE-code ABAQUS. Finally, the simulation results are compared with experimental results from the sintering of free as well as uniaxially loaded specimens. Copyright © 2000 John Wiley & Sons, Ltd.