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Mechanism of Ductility Improvement In L12 Compounds by Interstitial Elements

Published online by Cambridge University Press:  26 February 2011

T. K. Chaki
T. K. Chaki*
Affiliation:
State University of New York, Department of Mechanical and Aerospace Engineering, Buffalo, NY 14260
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Abstract

Interstitial boron atoms are known to increase room temperature ductility in Ni-rich Ni3Al and Ni3Si. Inerstitial carbon atoms increase ductility in Ni-rich Ni3Si, but not in Ni3Al. It is argued that grain boundary segregation of B or C is not the cause of the increase in ductility. Instead, strong Ni-B bonding and antisite Ni defects reduce the strength of directional Ni-Al bonding in ordered Ni3Al so that Ni and Al atoms can relax more easily to fill up the microcavities at the grain boundaries, thereby strengthening the boundaries. The reduced Ni-Al bonding will also enhance the ductility in the interior of the grains so that dislocations can be easily generated to shield the tips of the cracks at the grain boundary. In Ni3Si, strong Si-C bonds distort the directionality of Ni-Si bonding. Evidence for this model is presented. Estimates of the concentration of interstitial atoms to achieve maximum ductility are made and the estimate agrees well with the experimental value.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 213: Symposium Q – High-Temperature Ordered Intermetallic Alloys IV , 1990 , 769
Copyright
Copyright © Materials Research Society 1991

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References

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