Accession Number:

ADA285497

Title:

Multiphase Ceramics for Mechanical and Structural Reliability at Low and Elevated Temperatures

Descriptive Note:

Final rept. 15 Dec 1990-30 Jun 1994

Corporate Author:

LEHIGH UNIV BETHLEHEM PA MATERIALS RESEARCH CENTER

Report Date:

1994-06-30

Pagination or Media Count:

246.0

Abstract:

AFOSR project 91-0126 was undertaken to develop a design approach for improving the high-temperature structural reliability e.g., resistance to creep, fracture and grain growth and room temperature mechanical reliability e.g., flaw tolerance of structural ceramics. Some of the major accomplishments of this work are highlighted below 1. Engineering of the grain boundary chemistry in alumina resulted in a lowering of the creep rate by over two orders of magnitude by the addition of lOOOppm of Y2O3. It is conjectured that the presence of a highly segregated oversized similarly charged ion at the grain boundaries is responsible for inhibiting grain boundary diffusion and lowering the creep rate. 2. Duplex microstructures of A12O3YAG and A12O3ZrO2 exhibited lower creep rates and higher fracture toughness values than their single phase constituents. The creep data was well described by a composite creep equation developed for isostrain behavior i.e. the strain rates are the same for each phase. The higher fracture toughness was attributed to the contribution of low energy interphase boundaries to the overall composite toughness.

Subject Categories:

  • Ceramics, Refractories and Glass
  • Laminates and Composite Materials

Distribution Statement:

APPROVED FOR PUBLIC RELEASE