Accession Number:

ADA190399

Title:

Transformation Toughening of Ceramics.

Descriptive Note:

Annual rept. no. 2, 1 Sep 86-31 Aug 87,

Corporate Author:

ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER

Personal Author(s):

Report Date:

1987-10-01

Pagination or Media Count:

124.0

Abstract:

The mechanical properties of high toughness magnesia partially stabilized zirconia were found to be severely degraded by a single cooling cycle between room temperature and 196 C. In-situ Raman spectroscopy and optical interference measurements, and room temperature x-ray diffraction were used to correlate the changes in mechanical properties with structural changes cooling to temperatures below approximately -100C caused transformation of most of the tetragonal precipitates that are responsible for toughening to a new phase was stable with heating to 300 C, but at 400 C it transformed back to the tetragonal structure. After heating to 400 C the original high toughness mechanical properties were also restored. A new approach for measuring the nature and distribution of strains within transformation zones surrounding cracks in transformation toughened materials was demonstrated, using Mg-PSZ. The method involves measuring out-of-plane distortions adjacent to a surface-breaking crack and comparing the measurements with computed displacements. The fraction of transformation was found to be strongly varying function of distance from the crack plane.

Subject Categories:

  • Ceramics, Refractories and Glass

Distribution Statement:

APPROVED FOR PUBLIC RELEASE