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Slip, twinning, and fracture at a grain boundary in the L12 ordered structure—AΣ = 9 tilt boundary

Published online by Cambridge University Press:  31 January 2011

M. H. Yoo  and
A. H. King
M. H. Yoo
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
A. H. King
Affiliation:
Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
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Abstract

The role of interaction between slip dislocations and a Σ = 9 tilt boundary in localized microplastic deformation, cleavage, or intergranular fracture in the Li2 ordered structure has been analyzed by using the anisotropic elasticity theory of dislocations and fracture. Screw superpartials cross slip easily at the boundary onto the (1$\overline 1$1) and the (001) planes at low and high temperatures, respectively. Transmission of primary slip dislocations onto the conjugate slip system occurs with a certain degree of difficulty, which is eased by localized disordering. When the transmission is impeded, cleavage fracture on the ($\overline 1$11) plane is predicted to occur, not intergranular fracture, unless a symmetric double pileup occurs simultaneously. Absorption (or emission) of superpartials occurs only when the boundary region is disordered. Slip initiation from pre-existing sources near the boundary can occur under the local stress concentration. Implications of the present result on the inherent brittleness of grain boundaries in Ni3 Al and its improvement by boron segregation are discussed.

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Articles
Information
Journal of Materials Research , Volume 3 , Issue 5 , October 1988 , pp. 848 - 855
Copyright
Copyright © Materials Research Society 1988

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References

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