Observations on densification of Al-Al₂O₃ composite powder compacts by pressure cycling

Abstract

The effectiveness of pressure cycling on the consolidation of powder composites is investigated. Mixed Al and various amounts of Al₂O₃ powders were consolidated under static and cyclic pressure at room temperature in uniaxial consolidation experiments. The results showed that each pressure cycle increases green density and the cyclic effect is stronger when there is a relatively large volume fraction of Al₂O₃ powder. The compacts produced by pressure cycling have much higher strength than those produced with a single pressure excursion and the process ability of compacts should also improve via pressure cycling. Microscopic observations showed that greater uniformity is obtained in compacts by cyclic consolidation. The origin of the beneficial effect of pressure cycling is related to the deviatoric stresses generated by volumetric mismatch due to the different compressibilities of the phases.