Accession Number:

ADA224460

Title:

Dynamic Consolidation of Super Hard Materials

Descriptive Note:

Technical rept. 1 Oct 1988-31 Dec 1989,

Corporate Author:

CALIFORNIA INST OF TECH PASADENA SEISMOLOGICAL LAB

Report Date:

1990-06-25

Pagination or Media Count:

58.0

Abstract:

Shock consolidation experiments were conducted via flyer impact on synthetic diamond 6-12 microns and cubic boron nitride c-BN 4-8 microns admixed with SiC whisker, Si3N4 whisker, SiC powder and Si powder contained in stainless steel capsules in the shock pressure range 10-30 GPa. Scanning electron microscopy and transmission electron microscopy imaging of the samples revealed no plastic deformation or melting of diamond and virtually no deformation of c-BN, whereas the SiC and Si3N4 whiskers were extensively melted and recrystallized into bundle-shaped crystallites. In contrast, SiC powder mixed with diamond was also melted but demonstrated equant grain growth. A new mixture model of powder plus whisker materials is formulated on the basis of sphere-rod mixing and packing experiments. The model assigns excess porosity to the zone around whiskers and yields a better description of the energy deposition mechanism of the consolidation of powder-whisker systems. Some of the experiments employed Sawaokas post-shock annealing technique, in which the sample is sandwiched between two layers of a mixture of titanium powder plus carbon. Very well consolidated samples were obtained with post-shock heating under shock pressures of only about 12 GPa. jes

Subject Categories:

  • Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE