Crack-Growth Resistance of in Situ-Toughened Silicon Nitride

The fracture toughness of a commercial, hot‐pressed, in situ‐toughened silicon nitride with an elongated grain structure is determined by four different testing methods. The fracture toughness is found to be 5.76 ± 0.27, 8.48 ± 0.50, 10.16 ± 0.66, and 10.68 ± 0.39 Mpa.m1/2, respectively, by indentat...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1994-04, Vol.77 (4), p.1042-1046
Main Authors: Choi, Sung R., Salem, Jonathan A.
Format: Article
Language:English
Subjects:
360203 - Ceramics, Cermets, & Refractories- Mechanical Properties
Applied sciences
Building materials. Ceramics. Glasses
Ceramic industries
Chemical industry and chemicals
CRACK PROPAGATION
Crystal microstructure
DATA
Exact sciences and technology
EXPERIMENTAL DATA
FRACTURE PROPERTIES
Fracture testing
Grain size and shape
HEAT RESISTANT MATERIALS
Hot pressing
INFORMATION
MATERIALS
MATERIALS SCIENCE
MATERIALS TESTING
MECHANICAL PROPERTIES
MECHANICAL TESTS
MICROSTRUCTURE
NITRIDES
NITROGEN COMPOUNDS
NUMERICAL DATA
PNICTIDES
SILICON COMPOUNDS
Silicon nitride
SILICON NITRIDES
Strength of materials
Structural ceramics
Technical ceramics
TESTING
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Description
Summary:The fracture toughness of a commercial, hot‐pressed, in situ‐toughened silicon nitride with an elongated grain structure is determined by four different testing methods. The fracture toughness is found to be 5.76 ± 0.27, 8.48 ± 0.50, 10.16 ± 0.66, and 10.68 ± 0.39 Mpa.m1/2, respectively, by indentation crack size measurement, indentation strength, single‐edge‐precracked‐beam, and chevron‐notched‐beam methods. The discrepancy in fracture toughness between the testing methods is related to R‐curve behavior, as measured using the indentation strength technique. These results indicate that there is no unique fracture toughness value and that a fracture toughness testing method with appropriate qualifiers is needed for rising R‐curve materials. Therefore, care should be taken in interpreting and utilizing fracture toughness values evaluated from different testing methods if a material exhibits a rising R‐curve. Complete characterization of the R‐curve may be a prerequisite.
ISSN:0002-7820
1551-2916
DOI:10.1111/j.1151-2916.1994.tb07265.x