Characterization of complex die-pressed Al2O3 green compact using liquid immersion, X-ray tomography, and numerical simulations

This study examined the compaction behavior of a green ceramic component with a complex shape formed by die pressing at 50 MPa using spray-dried alumina. Compared to a simple cylindrical sample, the sample with a complex shape revealed a higher degree of microstructural inhomogeneity and crack formation. Granule deformation and pore distribution at different sample locations were observed by optical microscopy after infiltrating liquid into the voids of a green compact. The refractive index of the immersion liquid should be different slightly from that of alumina for better observations. X-ray micro-computed tomography was also used to visualize the pore distribution and crack shape. Numerical simulations based on the Drucker-Prager/Cap model were performed to distinguish the stress and displacement distribution within the compact. The significant stress gradient at the crack initiation point could explain crack formation, whereas the application of a higher pressure resulted in a further increase in stress gradient.