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A Tem Study of the Relationship Between Dislocation Structure and the Anomalous Temperature Dependence of the Flow Stress in Ordered Ni3 (Al,1%Ta).

Published online by Cambridge University Press:  26 February 2011

M. J. Mills ,
N. Baluc  and
H. P. Karnthaler
M. J. Mills
Affiliation:
Institut de Genie Atomique, École Polytechnique Fédérale, 1015 Lausanne, Switzerland. Present Address: Materials Department 8314, Sandia National Laboratories, Livermore, CA 94550, USA.
N. Baluc
Affiliation:
Institut de Genie Atomique, École Polytechnique Fédérale, 1015 Lausanne, Switzerland
H. P. Karnthaler
Affiliation:
Institut für Festförperphysik, University of Vienna, A-1090 Vienna, Austria
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Abstract

The anomalous increase in the yield strength of single crystals of Ni3AI(1%Ta) as a function of temperature has been correlated with the post-deformation substructure using weak beam TEM techniques. At low temperatures (77K), there is evidence for abundant cross-slip between (111) and (111). With increasing temperature, this conventional cross-slip process is gradually replaced by the formation of KW locks--straight screw segments which have crossslipped and completely dissociated on (010). This change in the mode of cross slip corresponds with the onset of the yield strength anomaly. At still higher temperatures (544K and 715K), the KW locks become mobile and bow out on (010). The density of dislocations on the cube plane also increases sharply at higher temperatures, even though deformation occurs principally by glide on the primary (111) based on slip trace analysis. These observations are inconsistent with the widely accepted cross slip pinning model and suggest that deformation occurs primarily by the motion of the non-screw components. A dislocation model is introduced which attempts to account for the observed dislocation configurations while remaining consistent with the yield strength and work hardening behavior of these alloys.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 133: Symposium H – High-Temperature Ordered Intermetallic Alloys III , 1988 , 203
Copyright
Copyright © Materials Research Society 1989

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References

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