HAL Id: jpa-00215872
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Submitted on 1 Jan 1974
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DISCUSSION
J. Poirier
To cite this version:
J. Poirier. DISCUSSION. Journal de Physique Colloques, 1974, 35 (C7), pp.C7-149-C7-149.
�10.1051/jphyscol:1974716�. �jpa-00215872�
DISCUSSION
Chairman : J. P. POIRIER
J. STEEDS. - Width of dissociation of dislocations treated by strain gradient elasticity theory.
P. SWANN. - Critical assessment for measuring stacking fault energies.
A. BENETEAU, N. CLEMENT and P. COULOMB. -
Measurement of stacking fault energies from z ~ ( T ) in Ni-Cr alloys.
DISCUSSION ABSTRACT : J. P. POIRIER.
1. Strain gradient elasticity theory. - Frank elabo- rates on the basic ideas underlying Steed's talk ; the problem is : within what distance could strain-gradient elasticity (curvature elasticity) become comparable in importance to classical elasticity in metals ? Long range unequal forces must exist over distances of a few b. Steeds points out that these may possibly arise from Friedel's oscillations.
2. Measurements of stacking-fault energies. - The various methods for measuring stacking fault energies, reviewed by Swann, measure in fact the width of a defect. As far as the mobility of dislocations is concern-
ed, the width of the dislocation is indeed the relevant physical parameter, but it should be known in the experimental conditions. Thus, Poirier recalls that no apparent splitting was observed in dislocations of several Cu-A1 alloys, after creep at high temperature, by Orlovh, Pahutova and Cadek, although splitting was observed at room temperature before the experiments, the width considerably varying with the A1 content.
Methods of determination of the stacking fault energy based on the variation of T,,, for cross-slip with T, are, in Friedel's opinion very interesting for several reasons : they give access to the width of the dislocation in the experimental conditions of tempe- rature and they can be applied to FCC alloys without having to worry about Suzuki effect. Beneteau, Cle- ment and Coulomb applied the zI,,(T) method to the determination of the stacking-fault energy of Ni and Ni-Cr alloys, using Escaig's model of cross-slip, and
- find a lower value than previously estimated. Alexander and Haasen, making reference to Seeger's and Wolf's model, point out that the use of the z1,,(T) method involves a critical assessment of the cross-slip model on which it is based.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1974716
