Development of refractory composites with improved fracture toughness. [MgCr/sub 2/O/sub 4/-ZrO/sub 2/]

Technical Report · Thu Aug 01 04:00:00 EDT 1985

OSTI ID:5362818

Singh, J P; Poeppel, R B; James, J J; Picciolo, J J

The effects of unstabilized ZrO/sub 2/ and W inclusions on the fracture surface energy and thermal-shock resistance of MgCr/sub 2/O/sub 4/ have been characterized. The fracture surface energy for MgCr/sub 2/O/sub 4/-ZrO/sub 2/ composites was observed to depend on the agglomerate particle size, size distribution, and volume fraction of the ZrO/sub 2/ inclusions. Large, nonuniformly distributed ZrO/sub 2/ inclusions tended to produce a relatively small increase in the fracture surface energy of MgCr/sub 2/O/sub 4/. The fracture surface energy increased with increasing ZrO/sub 2/ content to a maximum value of 24.5 J/m/sup 2/ at 16.5 vol % ZrO/sub 2/, and decreased as the ZrO/sub 2/ content increased further. The increase in fracture surface energy for MgCr/sub 2/O/sub 4/-W with increasing W content was monotonic for the range of composition studied (less than or equal to10.3 vol % W); a value of 26 J/m/sup 2/ was obtained for MgCr/sub 2/O/sub 4/-10.3% W composites. It is proposed that these fourfold increases in fracture surface energy result from the absorption of energy due to microcrack formation in the MgCr/sub 2/O/sub 4/ matrix, which results from the tensile stresses due to the mismatch in thermal expansion coefficient and/or elastic modulus between the matrix and inclusions. In addition, for MgCr/sub 2/O/sub 4/-ZrO/sub 2/ composites, a major cause of microcracking is the tetragonal ..-->.. monoclinic phase transformation of ZrO/sub 2/ and the associated volume expansion. Thermal quench experiments indicated substantial improvements in the thermal-shock resistance of MgCr/sub 2/O/sub 4/ with appropriate ZrO/sub 2/ and W additions. 31 refs., 12 figs., 3 tabs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5362818
• Report Number(s): ANL/FE-85-1; ON: DE86000257
• Country of Publication: United States
• Language: English

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ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
CHROMATES
CHROMIUM COMPOUNDS
COAL GASIFICATION PLANTS
COMPOSITE MATERIALS
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DATA
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INCLUSIONS
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MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
REFRACTORIES
STRESSES
TENSILE PROPERTIES
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THERMAL SHOCK
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TUNGSTEN
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES