Solution softening in spinel
- Los Alamos National Lab., NM (United States). Center for Materials Science
- Ford Motor Co., Dearborn, MI (United States). Scientific Research Lab.
- Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Materials Science and Engineering
Conclusions from this study are: 1. The critical resolved shear stress of MgO.nAl{sub 2}O{sub 3} spinel at a given temperature decreases dramatically, by almost two orders of magnitude, with increasing deviation form stoichiometry, i.e., as n increases from 1 to 3.5. 2. The CRSS is proportional to exp({minus}T/T{sub 0}) and to [V{sub c}]{sup {minus}2}, where T{sub 0} is a characteristic temperature and [V{sub c}] is the concentration of charge-compensating cation vacancies. 3. Slip on {l_brace}111{r_brace} planes is thought to occur between the Kagome cation Layers and the adjacent anion layers. Slip on {l_brace}101{r_brace} planes is slightly easier (and has a higher T{sub 0}) because the planes are more widely separated. 4. Slip in spinel does not require synchro-shear, unlike slip in the C15 AB{sub 2} Laves phase, which has identical metal atom positions to the cation positions in spinel. 5. The temperature dependence of the CRSS is analyzed in terms of a model based on partial dislocations overcoming a steep and high Peierls potential. Parameters for the model can be chosen to explain the observed values of T{sub 0} and the CRSS extrapolated to T = 0 K for both spinel and sapphire. Other models are possible. 6. The dependence of CRSS on [V{sub c}]{sup {minus}2} can be explained in terms of kink nucleation at cation vacancies.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 651149
- Report Number(s):
- CONF-980202--
- Journal Information:
- Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 4-5 Vol. 39; ISSN 1359-6462; ISSN SCMAF7
- Country of Publication:
- United States
- Language:
- English
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