DYNAMIC COMPACTION OF AL2O3-ZRO2 COMPOSITIONS

Shock compaction of Al2Os-ZrO2 binary and ternary powder compositions resulted in dense, one-piece samples without visible cracks for pressu res less-than-or-equal-to 12.6 GPa. Dynamic pressures were achieved by using a 6.5-m-long two-stage gas gun. It is believed that plastic def ormation by dislocation slip of alpha-Al2O3 partially accommodates the tensile stresses created during the release-of shock pressures. A fin e and narrow particle size distribution is necessary to achieve high b ulk densities, but the bulk structural integrity was not strongly rela ted to the distribution. A high-pressure phase of ZrO2, which was form ed from the monoclinic polymorph, was found at and above shock pressur e of 6.3 GPa. No evidence of the orthorhombic cotunnite structure was observed. Compaction of glassy and submicrocrystalline rapidly solidif ied starting materials showed good structural integrity, although the bulk density was relatively low. It is not clear what the densificatio n/bonding mechanism is in these materials, although it appears not to be plastic deformation. Microstructural analysis showed that fine and uniform microstructures are retained after compaction at appropriate d ynamic pressures for all compositions, with some interparticle cohesio n present.