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Dislocated cellular structures
xxiv
ABSTRACTS
OF ARTICLES
TO APPEAR IN ACTA MET
Besides the usual damping effect and the relativity effect which tend to limit the velocity of dislocations in a solid under conventional loading, an edge dislocation in a solid subject to shock loading with encounter on additional velocity limiting mechanism. This new dynamic effect is caused by the differential effects of local stress field of an edge dislocation on the particle velocities in the shock zone of material above and below the ship plane on which the edge dislocation lies. 9.
DISLOCATED
7, No. ii
finite body is calculated. If the radial distribution of the local dilatation caused by the concentration fluctuation is specified, the problem can be solved analytically. For the total elastic energy of the fluctuation or precipitate an extraordinarily simple result is obtained: the energy is given by the volume integral over the square of the dilatation minus the square of the mean dilatation. The simplicity of this result can be used with advantage when the influence of the elastic energy on coarsening phenomena or disperse order is to be discussed.
CELLULAR STRUCTURES
J. E. Morral*& M. F. Ashby+ Division of Engineering and Applied Physics, Harvard University, Cambridge, Mass. *Dept. of Metallurgy University of Connecticut Storrs, Connecticut +University Engineering Labs. Trumpington St. Cambridge, England Received August
i0, 1973
When grains or cells form periodic structures their arrangement can contain dislocations. These defects and their movements are illustrated on lattice graphs for two and three dimensional systems. The lattice graph is topologically equivalent to the cellular structure, containing information on the number of faces, edges and corners of each cell, yet it is easier to use than the cellular structure when illustrating dislocation climb or glide. Several examples of cellular dislocation motion are described in detail and their motion is related to grain growth cell division and deformation by grainboundary sliding. 10.
Vol.
THE ELASTIC BEHAVIOUR OF A SPHERICALLY SYMMETRIC CONCENTRATION FLUCTUATION IN A F I N I T E BODY
H. O. K. Kirchner II. Physikalisches Institut University of Vienna A-1090 Strudlhofgasse 4 Austria The elastic field of a spherically symmetric concentration fluctuation or precipitate in a
ii. MULTI-ION INTERACTIONS ORDERING OF CuPt
AND THE
Philip C. Clapp Ledgemont Laboratory Kennecott Copper Corporation Lexington, Massachusetts 02173 Received August
28, 1973
It is proven that the Llq ordering of CuPt requires at least foUr-ion tetrahedral interaction. The linear chain multi-ion interactions suggested by Harrison for simple metals apparently do not play a significant role in this system. It is further shown that no triplet interaction of any range or configuration can contribute to the ordering energy of any AB alloy close to stoichiometry if the A and B atom positions of the ordered structure are crystallographically equivalent. Finally a tetrahedral cluster model of ordering in CuPt is proposed which explains some of the recent observations of Irani and Cahn and also Mitchell, Paris and LeFevre. 12. ON THE ANELASTIC CREEP
CONTRIBUTION
TO
G.J. Lloyd & R. J. McElroy Dept. of Metallurgy, University of Oxford, Parks Road, Oxford, England Received July 24, 1973 It is shown that creep strain transients can be adequately described by invoking anelastic strain contributions to both primary creep and unloading transients at all stress levels. Recourse on internal stress
t o hypot-TEeses b a s e d is not necessary.
The suggestion is discussed in terms of available experimental data and good agreement is obtained with results from unloading experiments
ABSTRACTS
OF ARTICLES
TO APPEAR IN ACTA MET
Besides the usual damping effect and the relativity effect which tend to limit the velocity of dislocations in a solid under conventional loading, an edge dislocation in a solid subject to shock loading with encounter on additional velocity limiting mechanism. This new dynamic effect is caused by the differential effects of local stress field of an edge dislocation on the particle velocities in the shock zone of material above and below the ship plane on which the edge dislocation lies. 9.
DISLOCATED
7, No. ii
finite body is calculated. If the radial distribution of the local dilatation caused by the concentration fluctuation is specified, the problem can be solved analytically. For the total elastic energy of the fluctuation or precipitate an extraordinarily simple result is obtained: the energy is given by the volume integral over the square of the dilatation minus the square of the mean dilatation. The simplicity of this result can be used with advantage when the influence of the elastic energy on coarsening phenomena or disperse order is to be discussed.
CELLULAR STRUCTURES
J. E. Morral*& M. F. Ashby+ Division of Engineering and Applied Physics, Harvard University, Cambridge, Mass. *Dept. of Metallurgy University of Connecticut Storrs, Connecticut +University Engineering Labs. Trumpington St. Cambridge, England Received August
i0, 1973
When grains or cells form periodic structures their arrangement can contain dislocations. These defects and their movements are illustrated on lattice graphs for two and three dimensional systems. The lattice graph is topologically equivalent to the cellular structure, containing information on the number of faces, edges and corners of each cell, yet it is easier to use than the cellular structure when illustrating dislocation climb or glide. Several examples of cellular dislocation motion are described in detail and their motion is related to grain growth cell division and deformation by grainboundary sliding. 10.
Vol.
THE ELASTIC BEHAVIOUR OF A SPHERICALLY SYMMETRIC CONCENTRATION FLUCTUATION IN A F I N I T E BODY
H. O. K. Kirchner II. Physikalisches Institut University of Vienna A-1090 Strudlhofgasse 4 Austria The elastic field of a spherically symmetric concentration fluctuation or precipitate in a
ii. MULTI-ION INTERACTIONS ORDERING OF CuPt
AND THE
Philip C. Clapp Ledgemont Laboratory Kennecott Copper Corporation Lexington, Massachusetts 02173 Received August
28, 1973
It is proven that the Llq ordering of CuPt requires at least foUr-ion tetrahedral interaction. The linear chain multi-ion interactions suggested by Harrison for simple metals apparently do not play a significant role in this system. It is further shown that no triplet interaction of any range or configuration can contribute to the ordering energy of any AB alloy close to stoichiometry if the A and B atom positions of the ordered structure are crystallographically equivalent. Finally a tetrahedral cluster model of ordering in CuPt is proposed which explains some of the recent observations of Irani and Cahn and also Mitchell, Paris and LeFevre. 12. ON THE ANELASTIC CREEP
CONTRIBUTION
TO
G.J. Lloyd & R. J. McElroy Dept. of Metallurgy, University of Oxford, Parks Road, Oxford, England Received July 24, 1973 It is shown that creep strain transients can be adequately described by invoking anelastic strain contributions to both primary creep and unloading transients at all stress levels. Recourse on internal stress
t o hypot-TEeses b a s e d is not necessary.
The suggestion is discussed in terms of available experimental data and good agreement is obtained with results from unloading experiments