The study of dipoles in Cu—Al alloys using weak-beam electron microscopy

The mechanism of climb of dissociated dislocations in f.c.c. metals and alloys is not well understood. Climb of dislocations by absorption or emission of vacancies at existing jogs in dissociated dislocations has been observed using the “weak-beam” technique of electron microscopy, but the mechanism of nucleation of jogs is not clear. In this paper we report some results of experiments designed to study the nucleation problem, and more generally the mechanism of absorption of point defects under conditions of high supersaturation.Thin (111) sections of deformed single crystals of Cu-Al alloys, of various compositions, have been electron irradiated in an AEI EM7 HVEM up to 1 MeV, either at room temperature, or elevated temperatures up to 200°C, using a goniometer heating stage. Observations under weak beam conditions have been made a) in situ in the HVEM b) at 100kV in an JEM100B, following irradiation in the HVEM. Interstitials produced by the irradiation are expected to be preferentially attracted to the dislocations because of the strong dislocation-interstitial interaction.

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Weak-Beam Electron Microscopy

Progress in Transmission Electron Microscopy 1 - Springer Series in Surface Sciences ◽

10.1007/978-3-662-09518-8_8 ◽

2001 ◽

pp. 245-271

Author(s):

D. J. H. Cockayne

Keyword(s):

Electron Microscopy ◽

Beam Electron ◽

Weak Beam

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A weak-beam electron microscopy analysis of defect clusters in heavy-ion irradiated silver and copper

Philosophical Magazine ◽

10.1080/14786437408222073 ◽

1974 ◽

Vol 29 (4) ◽

pp. 813-828 ◽

Cited By ~ 39

Author(s):

M. L. Jenkins

Keyword(s):

Electron Microscopy ◽

Heavy Ion ◽

Beam Electron ◽

Defect Clusters ◽

Weak Beam ◽

Electron Microscopy Analysis ◽

Microscopy Analysis

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Weak-beam electron microscopy of nearly transverse grain boundaries

phys stat sol (a) ◽

10.1002/pssa.2210380243 ◽

1976 ◽

Vol 38 (2) ◽

pp. K107-K109

Author(s):

F. W. Schapink

Keyword(s):

Electron Microscopy ◽

Grain Boundaries ◽

Beam Electron ◽

Weak Beam

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Mechanism of climb of dissociated dislocations

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1980.0077 ◽

1980 ◽

Vol 371 (1745) ◽

pp. 213-234 ◽

Cited By ~ 20

Keyword(s):

Electron Microscopy ◽

Point Defects ◽

Electron Irradiation ◽

Elevated Temperatures ◽

Beam Electron ◽

Microscopy Technique ◽

Weak Beam ◽

High Supersaturation ◽

Edge Component ◽

The Individual

The ‘weak-beam’ electron microscopy technique has been used to study the climb of dissociated dislocations in a C u-13.43 % A1 alloy under conditions of high supersaturation of point defects introduced by electron irradiation at room and elevated temperatures. Prismatic loops (assumed to be of the interstitial type because of the dislocation ‘bias’) are found to be nucleated on the individual partials. The Burgers vectors of the nucleated loops are a function of the dislocation character, and are such as to minimize the elastic energy of the resultant configuration (partial plus loop), and to maximize the edge component of the loops. For orientations other than pure edge, climb involves the generation of Burgers vectors different from those of the original partials. The complex dislocation configurations formed by climb at elevated temperatures can be understood in terms of the nucleation of prismatic loops and their growth in directions controlled by the climb force on the parts of the prismatic loops not lying in the glide plane of the dislocations.

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