Impurity effects on the creep of polycrystalline magnesium and aluminum oxides at elevated temperatures. Technical progress report, December 19, 1975--December 18, 1976
The research described covers work on: (1) Viscous creep of fine-grained MgO doped with iron. (2) The effects of residual fluorine on diffusional creep and grain growth kinetics in polycrystalline MgO. (3) The effects of transition metal impurities and grain size on the creep of polycrystalline Al/sub 2/O/sub 3/. (4) The construction of creep deformation maps for polycrystalline MgO and Al/sub 2/O/sub 3/, pure and doped with iron. Some of the significant findings include: (1) Three well defined regimes have been identified for the diffusional creep of polycrystalline MgO and Al/sub 2/O/sub 3/, pure and doped with transition metal impurities: (1) cation grain boundary diffusion (2) cation lattice diffusion, (3) anion grain boundary diffusion. (2) Creep deformation maps have been developed for ambipolar diffusional creep and applied to pure and doped MgO and Al/sub 2/O/sub 3/. (3) Iron in solid solution enhances grain boundary diffusivities (cation and anion) in polycrystalline MgO in addition to magnesium lattice diffusion via the creation of cation lattice vacancies. (4) Residual fluorine in polycrystalline MgO leads to enhanced magnesium lattice and grain boundary diffusivities and hence to increased diffusional creep and grain growth rates. (5) Viscous Coble (diffusional) creep, which is rate-limited by oxygen grain boundary diffusion, has been identified in reduced iron-doped (2 cation percent) and double-doped (1/4 percent Mn and 1/4 percent Ti) polycrystalline Al/sub 2/O/sub 3/.
- Research Organization:
- Utah Univ., Salt Lake City (USA). Dept. of Materials Science and Engineering
- DOE Contract Number:
- EY-76-S-02-1591
- OSTI ID:
- 7334592
- Report Number(s):
- COO-1591-31
- Country of Publication:
- United States
- Language:
- English
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Impurity effects on the creep of polycrystalline magnesium and aluminum oxides at elevated temperatures. Technical progress report, December 19, 1972--December 18, 1973
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Related Subjects
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CREEP
CRYSTAL STRUCTURE
CRYSTALS
DOPED MATERIALS
ELEMENTS
FLUORINE
GRAIN GROWTH
GRAIN SIZE
HALOGENS
IMPURITIES
IRON
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
NONMETALS
OXIDES
OXYGEN COMPOUNDS
POLYCRYSTALS
SIZE
TRANSITION ELEMENTS