Controlled Ceramic-Ceramic Eutectic Microstructures
Final rept. 1969-1976
PENNSYLVANIA STATE UNIV UNIVERSITY PARK
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Preparation, microstructure, crystallography and mechanical properties of high melting oxide eutectics are described. It is shown that the microstructure can be predicted from the volume fraction of the minor phase. Two basic criteria control the interface and crystallographic orientation i minimization of the misfit between oxygen sublattices ii neutralization of ionic charge across the interfacial plane. The fracture strength is related to the colony size and decreases only slightly from room temperature to 1600 C. The fracture surface energy does not exhibit any dependence on fiber spacing. Knoop microhardness is greater than that of either the magnesia or spinel separately. The creep resistance of the grain microstructure is greater than that of the colony microstructure and MgAl2O4 single crystal. A void nucleation and growth mechanism may best describe the deformation process with eutectic ingots containing colonies or grains.
- Ceramics, Refractories and Glass
- Laminates and Composite Materials
- Solid State Physics