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Cleavage Fracture and Dislocation Structures of Ductile L12 Type Ni3Ge Single Crystals

Published online by Cambridge University Press:  26 February 2011

H.R.P. Inoue ,
C.M. Wayman  and
T. Saburi
H.R.P. Inoue
Affiliation:
University of Illinois,Department of Materials Science and Engineering, Urbana, IL 61801
C.M. Wayman
Affiliation:
University of Illinois,Department of Materials Science and Engineering, Urbana, IL 61801
T. Saburi
Affiliation:
Osaka University, Department of Materials Science and Engineering, Suita, Osaka 565, Japan
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Abstract

Fracture and dislocation structures of single crystals of the L12-type compound Ni3Ge deformed in tension-compression at room temperature are investigated by optical and electron microscopy. After considerable plastic deformation, cracks nucleate along primary (111) planes of [245]-oriented single crystals and grow in zigzag manner by connecting one octahedral plane to another. Fracture occurs by brittle cleavage. Similar cleavage fracture also occurs when thin films (whose plane is (111)) prepared from cyclically deformed specimens are further deformed at room temperature. These observations are different from those reported in a previous study where the cleavage plane is claimed to be {001} for single crystals deformed in tensio at room temperature. A number of piled-up dislocations are emitted due to stress concentration at and ahead of crack tips, evidencing that this compound is intrinsically ductile. Superlattice intrinsic stacking faults are observed in front of crack tips along with a moire structure. Although there is argument that such moire structures are formed in persistent slip bands during cyclic deformation of Ni3Al, this is unlikely in the present case. The moire structure observed is believed to be formed by deformation of the thin (111) film.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 213: Symposium Q – High-Temperature Ordered Intermetallic Alloys IV , 1990 , 521
Copyright
Copyright © Materials Research Society 1991

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References

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