Densification and Microstructure of the CAP'd Chromium Powder Compact

High temperature consolidation of chromium powder in a vacuum-scaled glass mould under atmospheric pressure (CAP of chromium powder) was studied. Densification and microstructural development during the CAP process were investigated by the density measurement and the structural observations on the CAP'd compacts. The CAP process was found to be effective for the densifying chromium powder compact at sufficiently low temperatures. The CAP'd compact was observed to have a characteristic three-layer structure; the glass-penetrating outer layer, intermediate porous layer and dense core. The pore surfaces were covered with thin glassy film, and polyhedral particles, the main component of which was confirmed to be chromium, distributed in the dense core region. These particles were observed to be formed at the pore surfaces and they seemed to grow until they filled the pore volume, eventually dissolve into the chromium matrix. The densification was supposed to proceed from the central region of the compacts towards the outer layers, with squeezing the glassy film wetted over the pore surfaces.