Density gradients and springback: environmental influences

Laser dilatometry was combined with X-ray computed tomography (XRCT) to investigate the relationship between springback and internal density gradients in dry-pressed alumina compacts. Compacts were prepared using the same binder and binder content but different states of plasticization to examine these effects on dimensions and final density distribution. Both density gradients and microstructural-level characteristics exert control over differential springback behavior; the expansion of the low-density (LD) zone is larger than that of the high-density (HD) zone. For these submicron alumina powders, the concentration of binder associated with density gradients leads to potential loss of final dimensional tolerance. A sinusoidal dimensional response, dependent upon the state of the binder, is noted, which changes dramatically with time and environmental exposure. In some cases, dimensional changes occurred due to moisture absorption/desorption in compacts prepared at relative humidities different from ambient conditions.