Fracture and R-curves in high-volume fraction Al2O3/Al composites

Nagendra, N. ; Jayaram, Vikram (2000) Fracture and R-curves in high-volume fraction Al2O3/Al composites Journal of Materials Research, 15 (5). pp. 1131-1144. ISSN 0884-2914

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Official URL: http://www.mrs.org/s_mrs/sec_subscribe.asp?CID=228...

Related URL: http://dx.doi.org/10.1557/JMR.2000.0161

Abstract

Fracture toughness and fracture mechanisms in Al2O3/Al composites are described. The unique flexibility offered by pressureless infiltration of molten Al alloys into porous alumina preforms was utilized to investigate the effect of microstructural scale and matrix properties on the fracture toughness and the shape of the crack resistance curves (R-curves). The results indicate that the observed increment in toughness is due to crack bridging by intact matrix ligaments behind the crack tip. The deformation behavior of the matrix, which is shown to be dependent on the microstructural constraints, is the key parameter that influences both the steady-state toughness and the shape of the R-curves. Previously proposed models based on crack bridging by intact ductile particles in a ceramic matrix have been modified by the inclusion of an experimentally determined plastic constraint factor (P) that determines the deformation of the ductile phase and are shown to be adequate in predicting the toughness increment in the composites. Micromechanical models to predict the crack tip profile and the bridge lengths (L) correlate well with the observed behavior and indicate that the composites can be classified as (i) short-range toughened and (ii) long-range toughened on the basis of their microstructural characteristics.

Item Type:Article
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ID Code:13619
Deposited On:12 Nov 2010 15:14
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