Accession Number:

ADA014922

Title:

Diffusion Controlled Deformation of Particulate Composites.

Descriptive Note:

Technical rept.,

Corporate Author:

STANFORD UNIV CALIF DEPT OF MATERIALS SCIENCE AND ENGINEERING

Report Date:

1975-08-01

Pagination or Media Count:

39.0

Abstract:

Unusual mechanical effects at elevated temperatures have been observed in a model composite system of zinc containing large volume fractions 0.05 to 0.30 of small 1 micrometer Al3O3 or W particles. These materials are dispersion-weakened in the temperature range 0.3 T sub m to 0.7 T sub m, and show marked insensitivity of flow stress to changes in strain rate or temperature at about 0.7 T sub m. Strain-aging yield points are also observed at 0.6 T sub m. An explanation for such behavior proposes that, above a threshold stress, mobile dislocations are generated at particle-matrix interfaces by local incompatibility stresses, and that these dislocations have a dominant effect on the nominal flow stress in the region 0.3 to 0.7 T sub m. A constitutive equation reminiscent of the Ansell-Weertman theory for creep of dispersion-strengthened materials is derived from the model, and compared with experimental creep data.

Subject Categories:

  • Laminates and Composite Materials

Distribution Statement:

APPROVED FOR PUBLIC RELEASE