Numerical simulation of anisotropy in sintering due to prior compaction

The anisotropic sintering of precompacted powders can be attributed partial ly to the morphological characteristics of the pores developed during compa ction. To support this idea we simulate a two-dimensional periodic arrangem ent of particles in two steps: compaction using finite elements, and surfac e/grain boundary sintering using finite differences. These simulations indi cate that, for "clean" powders, anisotropy in neck size as a result of comp action results in anisotropy in sintering with higher shrinkage along the t ransverse direction than in the direction of compaction. If the maximum com pressive stress is high enough to disturb the surface oxide preferentially at contacts normal to the compaction direction, then enhanced grain boundar y diffusion at these locations can lead to a reversal of the anisotropy, in agreement with experimental observations.