Transformation Toughening of Ceramics
Abstract
The results of a three-year study, aimed at understanding factors that dictate microstructural evolution and mechanical properties of transformation toughened ceramics, are summarized. Large crack growth resistance curves (rather than single valued toughness) were discovered in toughened zirconia, and these were shown to be responsible for strength-toughness relations, damage tolerance, and other mechanical properties. New insight was gained into mechanisms of controlling grain growth during processing, and a method for forming high strength, fine grained ZrO2 fibers was discovered. In the final year's work, which is reported in detail here, a new tetragonal-to-orthorhomic phase transformation at low temperatures was discovered and shown to have a dramatic effect on mechanical properties. New methods were applied to measure the amount and location of phase transformation within crack tip zones and to quantify crack tip shielding, evaluate stability and reversibility of the martensitic transformation, and to determine the net transformation strain that gives to toughening. Finally, crack growth under cyclic loading was demonstrated to be important in zirconia materials.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1988
- Accession Number
- ADA204687
Entities
People
- D. B. Marshall