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Title: Microstructural development in CaO-MgO-ZrO sub 2

Abstract

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.

Authors:
Publication Date:
Research Org.:
Case Western Reserve Univ., Cleveland, OH (USA)
OSTI Identifier:
6110083
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph. D.)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALCIUM OXIDES; MICROSTRUCTURE; MAGNESIUM OXIDES; ZIRCONIUM OXIDES; ELECTRON MICROSCOPY; HEAT TREATMENTS; MORPHOLOGY; PHASE TRANSFORMATIONS; POLYCRYSTALS; PRECIPITATION; ALKALINE EARTH METAL COMPOUNDS; CALCIUM COMPOUNDS; CHALCOGENIDES; CRYSTAL STRUCTURE; CRYSTALS; MAGNESIUM COMPOUNDS; MICROSCOPY; OXIDES; OXYGEN COMPOUNDS; SEPARATION PROCESSES; TRANSITION ELEMENT COMPOUNDS; ZIRCONIUM COMPOUNDS; 360602* - Other Materials- Structure & Phase Studies

Citation Formats

Dickerson, R M. Microstructural development in CaO-MgO-ZrO sub 2. United States: N. p., 1989. Web.
Dickerson, R M. Microstructural development in CaO-MgO-ZrO sub 2. United States.
Dickerson, R M. Sun . "Microstructural development in CaO-MgO-ZrO sub 2". United States.
@article{osti_6110083,
title = {Microstructural development in CaO-MgO-ZrO sub 2},
author = {Dickerson, R M},
abstractNote = {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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1989},
month = {1}
}

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