Creep and Stress Rupture Behavior of an Advanced Silicon Nitride: Part I, Experimental Observations |
| |
Authors: | Mamballykalathil N. Menon Ho T. Fang David C. Wu Michael G. Jenkins Mattison K. Ferber Karren L. More Camden R. Hubbard Theodore A. Nolan |
| |
Affiliation: | AlliedSignal Engines, AilledSignal Aerospace Company, Phoenix, Arizona 85072;Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195;High Temperature Materials Laboratory, Oak Ridge National Laboratoty, Oak Ridge, Tennessee 37831 |
| |
Abstract: | Cylindrical buttuohead specimens of an advanced silicon nitride were tested in uniaxial tension at temperatures between 1422 and 1673 K. In the range 1477 to 1673 K, creep deformation was reliably measured using high-temperature contact probe extensometry. Extensive scanning and transmission electron microscopy has revealed the formation of lenticular cavities at two-grain junctions at all temperatures (1422–1673 K) and extensive triple-junction cavitation occurring at the higher temperatures (1644–1673 K). Cavitation is believed to be part of the net creep process. The stress rupture data show stratification of the Monkman–Grant lines with respect to temperature. Failure strain increased with increase in rupture time or temperature, or decrease in stress. Fractography showed that final failure occurred by subcritical crack growth in all specimens. |
| |
Keywords: | |
|
|