Numerical modeling of solid state sintering using heterogeneous packing and diffusion processes

Physical modeling and computer simulation for the description of solid state low stresses sintering process have been performed. The first step consists in fitting heterogeneous particles together in a three-dimensional virtual box, with shape and size distributions given as parameters. These particles are then submitted to gravity, contact boundary conditions, friction forces, and Van Der Waals interaction. Thus, one dispose of a realistic dense packing. Starting from size distribution and fitting parameters, it is then possible to obtain the same densities and the same configurations as those observed in the real case. The densification process is then simulated. The constitutive model is based on volume, surface, grain boundary and gaseous diffusion, using laws derived from local energetic considerations and avoiding strong hypothesis. This approach allows to validate work on sintering theory, based on particular cases or with unchecked assumptions. Important post-processing investigations let us to identify constants and pertinent options for the homogenization problem which will led us to a macroscopic description of the sintering process. The paper describes laws and algorithms used in the proposed modeling. Results are shown to illustrate solid state sintering of powder aggregates.