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) : Marshall, D B

PDF Url : ADA190399

Report Date : Oct 1987

Pagination or Media Count : 124

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

Distribution Statement : APPROVED FOR PUBLIC RELEASE