R-curve behavior and flaw insensitivity of Ce-TZP/Al[sub 2]O[sub 3] composite

A ceria-partially-stabilized zirconia-alumina (Ce-TZP/Al[sub 2]O[sub 3]) composite optimized for transformation toughening was used to demonstrate its flaw insensitivity due to R-curve behavior. Four-point bend specimens fabricated with a controlled distribution of spherical pores showed nearly the...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1993-04, Vol.76:4
Main Authors: Ramachandran, N., Chao, Luen Yuan, Shetty, D.K.
Format: Article
Language:English
Subjects:
360603 - Materials- Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CERIUM
CHALCOGENIDES
COMPOSITE MATERIALS
CRACK PROPAGATION
CRACKS
DEFECTS
DIMENSIONS
DOPED MATERIALS
ELEMENTS
FRACTURE PROPERTIES
LENGTH
MATERIALS
MATERIALS SCIENCE
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
POROSITY
RARE EARTHS
REINFORCED MATERIALS
SINTERED MATERIALS
STABILIZATION
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES
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Description
Summary:A ceria-partially-stabilized zirconia-alumina (Ce-TZP/Al[sub 2]O[sub 3]) composite optimized for transformation toughening was used to demonstrate its flaw insensitivity due to R-curve behavior. Four-point bend specimens fabricated with a controlled distribution of spherical pores showed nearly the same characteristic strength and strength variability (Weibull modulus) as specimens fabricated without the artificial pores. In situ observations confirmed stable growth of cracks initiated at pores and the crack lengths at fracture instability were much greater than the pore sizes, thus resulting in fracture strengths insensitive to the pores. The small variability in the fracture strength was found to be associated with variability in the R-curve and the instability crack lengths. An analysis based on the fracture instability criterion for rising crack growth resistance accounted for the strength variability due to variability in the R-curve. Comparable four-point bend experiments were also conducted on a sintered yttria-partially-stabilized zirconia (2Y-TZP) ceramic. This ceramic showed significant degradation of strength due to the presence of the pores. This flaw sensitivity is attributed to its steep rising R-curve over short crack lengths.
ISSN:0002-7820
1551-2916
DOI:10.1111/j.1151-2916.1993.tb05320.x