Impurity effects on the creep of polycrystalline magnesium and aluminum oxides at elevated temperatures. Technical progress report, December 19, 1974--December 18, 1975
Work is reported on: 1. Viscous creep of fine-grained MgO doped with iron. 2. The effects of transition metal impurities and grain size on the creep of polycrystalline Al/sub 2/O/sub 3/. 3. The non-viscous creep of large grain size MgO and Al/sub 2/O/sub 3/, pure and doped with transition metal impurities. 4. Stress relaxation tests on polycrystalline MgO and Al/sub 2/O/sub 3/, pure and doped with transition metal impurities. 5. The construction of creep deformation maps for polycrystalline MgO and Al/sub 2/O/sub 3/, pure and doped with iron. 6. Preliminary studies on the effect of grain size on the creep of polycrystalline mullite. Some of the significant findings include: 1. Power law creep (N approx. 3) in polycrystalline MgO is independent of iron doping, grain size, and oxygen partial pressure. 2. 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. 3. 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/. Stress relaxation deformation tests can be used to (1) identify transitions between viscous and non-viscous deformation, and (2) achieve high stresses (approx. 10/sup 3/ kg/cm/sup 2/) and strain rates (1h/sup -1/) without fracture. Good agreement exists between dead-load creep and stress relaxation studies in four point bending. (auth)
- Research Organization:
- Utah Univ., Salt Lake City (USA). Div. of Materials Science and Engineering
- OSTI ID:
- 7357410
- Report Number(s):
- COO-1591-29
- Country of Publication:
- United States
- Language:
- English
Similar Records
Impurity effects on the creep of polycrystalline magnesium and aluminum oxides at elevated temperatures. Technical progress report, December 19, 1972--December 18, 1973
Impurity effects on the creep of polycrystalline magnesium and aluminum oxides at elevated temperatures. Technical progress report, December 19, 1978-December 18, 1979
Related Subjects
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CREEP
CRYSTAL STRUCTURE
CRYSTALS
GRAIN SIZE
IMPURITIES
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MECHANICAL PROPERTIES
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
POLYCRYSTALS
RESEARCH PROGRAMS
SIZE
STRESS RELAXATION