Creep of Polycrystalline MgO-FeO-Fe2O3 Solid Solutions |
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Authors: | R T TREMPER R A GIDDINGS J D HODGE R S GORDON |
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Affiliation: | Division of Materials Science and Engineering, College of Engineering, University of Utah, Salt Lake City, Utah 84112 |
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Abstract: | Steady-state creep experiments were performed on hot-pressed polycrystalline MgO doped with Fe. Dead-load 4-point bend creep tests were conducted at stresses of 26 to 270 kg/cm2, at temperatures of 1250° to 1450°C, in O2 partial pressures of 1 to 10−9 atm, on specimens with grain sizes of 10 to 65 μm. Viscous steady-state creep was always observed when the grain size was stable. Experiments at variable P O2's and temperatures were used to identify regimes of high (117 ± 10 kcal/mol) and low (81 ± 5 kcal/mol) activation energy. In the latter, creep rates were nearly independent of Fe dopant concentration and P O2, whereas in the former creep rates were enhanced by increasing P O2's and Fe dopant levels. The high- and low-activation-energy regimes were interpreted as diffusional creep controlled primarily by Mg lattice diffusion and O grain-boundary diffusion, respectively. |
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