Microstructural development in CaO-MgO-ZrO sub 2
Thesis/Dissertation
·
OSTI ID:6110083
Matrix and precipitate microstructures in various CaO-MgO-ZrO{sub 2} poly-crystalline ceramics were studied subsequent to heat treatments at 1400{degree}C of up to 50 hours after sintering. CaO/MgO solute mole ratios of 85/15, 70/30, 50/50, 30/70, and 15/85 were used in 90.5 m/o ZrO2 materials to explore composition-dependent precipitation stress effects on intragranular t-ZrO{sub 2} precipitate morphologies. Strain-induced coarsening effects led to layering of individual precipitates by variant in some samples and the formation of a tri-variant trigonal bipyramid morphology in the most CaO-rich alloy. Strain energy calculations assuming plate-shaped precipitates were performed to compare with the observed precipitate-lattice habit planes. A high resolution electron microscopy study showed step-wise growth of orthorhombic and monoclinic ZrO{sub 2} product phases with transformation in thin foils. Modest evidence of a room temperature isothermal tetragonal to monclinic transformation was obtained. The initially homogeneous precipitate-matrix microstructure was observed to undergo phase separation through preferential coarsening of tetragonal precipitates along grain boundaries in conjunction (in CaO-rich materials) with a liquid film migration phenomenon, creating solute rich precipitate-free zones at neighboring boundaries.
- Research Organization:
- Case Western Reserve Univ., Cleveland, OH (USA)
- OSTI ID:
- 6110083
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CRYSTAL STRUCTURE
CRYSTALS
ELECTRON MICROSCOPY
HEAT TREATMENTS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MICROSCOPY
MICROSTRUCTURE
MORPHOLOGY
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
POLYCRYSTALS
PRECIPITATION
SEPARATION PROCESSES
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES
360602* -- Other Materials-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CRYSTAL STRUCTURE
CRYSTALS
ELECTRON MICROSCOPY
HEAT TREATMENTS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MICROSCOPY
MICROSTRUCTURE
MORPHOLOGY
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
POLYCRYSTALS
PRECIPITATION
SEPARATION PROCESSES
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES