Abstract
The microstructural variables that determine the toughness (T-curve) characteristics of alumina and other structural ceramics are considered. Alumina ceramics gain their toughness from shielding by grain-interlock bridging at the interface behind the crack tip. A general fracture mechanics formalism for describing the bridging is outlined in terms of desirable microstructural elements, such as weak internal boundaries, high internal stress, coarse microstructure. The T-curve imparts the quality of flaw tolerance to the strength properties. We examine this quality, under both inert and interactive environmental conditions, monotonic and cyclic loading, using indentation flaws. In situ observations of bridging sites during loading in the scanning electron microscope provide insight into the bridge degradation micromechanisms. Finally, short-crack properties, spontaneous microcracking and wear degradation, are examined in light of the bridging model. It is concluded that design with ceramics may require certain tradeoffs, long vs short cracks, high strength vs flaw tolerance, etc. The key to optimal performance in ceramics rests with microstructural processing for specific properties.
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© 1991 Springer Science+Business Media Dordrecht
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Bennison, S.J., Rödel, J., Lathabai, S., Chantikul, P., Lawn, B.R. (1991). Microstructure, Toughness Curves and Mechanical Properties of Alumina Ceramics. In: Shah, S.P. (eds) Toughening Mechanisms in Quasi-Brittle Materials. NATO ASI Series, vol 195. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-3388-3_13
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DOI: https://doi.org/10.1007/978-94-011-3388-3_13
Publisher Name: Springer, Dordrecht
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