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Analysis of Weak-Beam Contrast from SESF/SISF Fault Pairs Associated with ½ <112] Superdislocations in TiAl

Published online by Cambridge University Press:  10 February 2011

Mukul Kumar ,
S. Sriram ,
Adam J. Schwartz  and
Vijay K. Vasudevan
Mukul Kumar
Affiliation:
Lawrence Livermore National Laboratory, Univ. of California, L-370, Livermore, CA 94550
S. Sriram
Affiliation:
Novellus Systems, Inc., 3970 N First St., San Jose, CA 95134
Adam J. Schwartz
Affiliation:
Lawrence Livermore National Laboratory, Univ. of California, L-370, Livermore, CA 94550
Vijay K. Vasudevan
Affiliation:
Dept. of Materials Science & Engineering, Univ. of Cincinnati, Cincinnati, OH 45221–0012
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Abstract

The diffraction contrast from dissociated ½<112] superdislocations in γ-TiAl intermetallic alloy cannot always be analyzed using conventional rules of diffraction contrast. In particular, the configuration involving three similar Shockley partials on adjacent planes has often been ruled out due to the absence of fringes indicating the presence of stacking faults. In order to determine the dissociated configuration, weak-beam transmission electron microscope observations of edge-oriented ½<112] superdislocations have been correlated with computer simulated images. Dissociation of these superdislocations into three similar ⅙<112] partial dislocations bounding a superlattice extrinsic and intrinsic stacking fault pair has been consequently determined from these analyses. It has been found that diffraction contrast alone cannot distinguish between the various configurations that lead to the formation of the fault pair, but the formation of an antiphase boundary or complex stacking fault linked dissociation or locking by stair rod dislocations can be ruled out.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 552: Symposium KK – High-Temperature Ordered Intermetallic Alloys VIII , 1998 , KK8.19.1
Copyright
Copyright © Materials Research Society 1999

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