Effect of Time and Temperature on Transformation Toughened Zirconias.
ARMY LAB COMMAND WATERTOWN MA MATERIAL TECHNOLOGY LAB
Pagination or Media Count:
The effects of exposure to elevated temperatures 900 to 1300 C for times ranging from 50 to 500 hours on toughened oxide ceramics intended for use in heat engines were examined. The materials were magnesia stabilized transformation toughened zirconia, yttria stabilized tetragonal zirconia polycrystal, and zirconia toughened alumina, as well as untoughened zirconias for comparison. The materials were heat treated, and physical and mechanical properties were then measured at room temperature. High temperature mechanical tests performed were stress rupture and stepped temperature stress rupture. The results of the tests indicate that the mechanical properties of magnesia stabilized transformation toughened zirconia degrade substantially after relatively short times at the moderate temperatures expected in low heat rejection diesel engines. The yttria stabilized tetragonal zirconia polycrystal and the untoughened partially stabilized zirconia materials appear to be more stable against the effects of time at temperature.
- Ceramics, Refractories and Glass