Localized Densification during the Stage II–III Transition - Compaction Efficiency at High Pressures

Localized densification and compaction efficiency at high pressures was studied using X-ray computed tomography. Stage III begins with the initiation of a region of uniform average density within the overall high-density zone. No further densification occurs in this region; additional pressure is transmitted into adjacent, less-dense zones and the die wall. This localized increase in wall friction continuously decreases compaction efficiency. Discrete element modeling was used to visualize force transfer. The transition was governed by events that ranged from the microscale to the macroscale. Terapascal levels of pressure were required to produce a uniform compact.