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Quantitative Evaluation of Crack Bridging in Fully Lamellar Ti-48A1-2Cr-2Nb

Published online by Cambridge University Press:  22 February 2011

D. J. Wissuchek ,
G. E. Lucas  and
A. G. Evans
D. J. Wissuchek
Affiliation:
Materials Department, University of California, Santa Barbara, CA 93106
G. E. Lucas
Affiliation:
Materials Department, University of California, Santa Barbara, CA 93106
A. G. Evans
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138
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Abstract

The toughening effect of ligaments in a fully lamellar Ti-48Al-2Cr-2Nb alloy has been determined by evaluation of J integrals of the crack tip and crack wake regions from surface strain maps. The crack tip fracture toughness KtiP was found to vary with lamellae orientation and ranged from Ktip = 13 MPa√m for inter-lamellar fracture to Ktip = 19.5 MPa√m for translamellar fracture The bridging contribution to fracture toughness was found to arise from a bimodal distribution of ligament sizes. Fracture surface reconstructions showed a distribution of large hinges that initiated at grain or subcolony boundaries and smaller ligaments associated with delaminations within a grain. The stress-displacement functions for these two ligament populations have been determined from a large scale bridging analysis of the resistance curves along with fractographic information. The small ligamerts appear to account for the initial rapid rise in crack growth resistance; and the large hinges, for the slow continued rise in toughness at large crack extensions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 364: Symposium L – High-Temperature Ordered Intermetallic Alloys–VI , 1994 , 481
Copyright
Copyright © Materials Research Society 1995

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