New interpretation for the origin of the anisotropic sintering shrinkage of AISI 316L rings based on the anisotropic stress field occurred on uniaxial cold compaction

AISI 316L powder mix was sieved in three particle sizes and successively compacted on rings with two different H/(D ext -D int ) ratios. The height and diameters were measured by a CMM at the green and at the sintered state. The shrinkage was calculated to study the influence of particle size and geometry on the anisotropy of dimensional change. As expected, the volumetric shrinkage increases moving from coarser to finer particle size, and the measurements confirmed the anisotropy of the dimensional variation. The measurements revealed that the lowest rings shrink more than the taller rings. The reference to the radial and axial stress during prior cold compaction shows an interesting correlation, in which shrinkage increases on increasing the stress. The further investigation of the deviatoric stress and the deviatoric shrinkage provided a possible explanation of the anisotropy of dimensional change on sintering as a function of the inhomogeneity of the compaction stress.