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.
Descriptors:
- *CERAMIC MATERIALS
- COOLING
- CRACKS
- DISTORTION
- MAGNESIUM OXIDES
- MECHANICAL PROPERTIES
- OPTICAL PROPERTIES
- RAMAN SPECTROSCOPY
- STABILIZATION
- STRUCTURAL PROPERTIES
- TEMPERATURE
- TOUGHNESS
- X RAY DIFFRACTION
- ZIRCONIUM OXIDES
- PHASE TRANSFORMATIONS
- MARTENSITE
- MAGNESIUM
- ZIRCONIUM
- MICROSTRUCTURE
- RAMAN SPECTROSCOPY
Subject Categories:
- Ceramics, Refractories and Glass