Thermally Activated Motion of a Screw Dislocation Overcoming the Peierls Potential for Prismatic Slip in an hcp Lattice

The interaction between interstitial oxygen atoms and <a>-type screw dislocations was investigated via first-principles calculations to elucidate the effect of oxygen solutes on the deformation behaviors of Mg. The results show that repulsive interactions exist between basal screw dislocation cores and oxygen atoms, which would enable the full basal dislocation to bypass the oxygen atoms in the dislocation glide plane through the cross-slip process. This repulsion also increases the resistance to the motion of dissociated basal dislocations. Moreover, the energy of prismatic <a>-type screw dislocation cores is reduced by the presence of oxygen, which would stabilize the screw dislocation core on the prismatic plane, accordingly facilitating the prismatic slip. This information can complement the fundamental knowledge of alloying Mg using interstitial solutes.

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Thermally Activated Nature of Basal and Prismatic Slip in Mg and Its Alloys

Magnesium Technology 2021 - The Minerals, Metals & Materials Series ◽

10.1007/978-3-030-65528-0_9 ◽

2021 ◽

pp. 53-60

Author(s):

Mohammed A. Shabana ◽

Jishnu J. Bhattacharyya ◽

Marek Niewczas ◽

Sean R. Agnew

Keyword(s):

Prismatic Slip ◽

Thermally Activated

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Thermally Activated motion of a Screw Dislocation in a Model B.C.C. Crystal

Journal of the Physical Society of Japan ◽

10.1143/jpsj.38.480 ◽

1975 ◽

Vol 38 (2) ◽

pp. 480-487 ◽

Cited By ~ 31

Author(s):

Shin Takeuchi ◽

Eiichi Kuramoto

Keyword(s):

Screw Dislocation ◽

Thermally Activated

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Dynamical Interaction between Thermally Activated Glide of Screw Dislocation and Self-Interstitial Clusters in Bcc Fe

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.139.59 ◽

2008 ◽

Vol 139 ◽

pp. 59-64 ◽

Cited By ~ 1

Author(s):

X.Y. Liu ◽

S.B. Biner

Keyword(s):

Screw Dislocation ◽

Constant Strain Rate ◽

Strain Rates ◽

Dislocation Mechanism ◽

Dynamical Interaction ◽

Thermally Activated ◽

Interaction Processes ◽

Junction Formation ◽

Dynamics Simulations ◽

Eam Potential

Constant strain rate molecular dynamics simulations under the modified boundary conditions were performed to elucidate the interaction processes between the kink motion of screw dislocation and the glissile self-interstitial atom cluster loops in bcc Fe by using an EAM potential for Fe fitted to ab initio forces. The junction formation and the helical dislocation mechanisms were identified as two possible interaction processes. In the junction mechanism, the initial Burgers vector 1/2<111> of the cluster loop was transformed into <100>. In the helical dislocation mechanism first the absorption, followed by the formation of the helical dislocation and the emission of the cluster loop through Hirsch mechanism was observed. Substantial hardening was seen as result of the interactions. The stress-strain plots obtained for different loop sizes, temperature and strain rates were used to estimate the strengthening factors.

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A CRITICAL REVIEW OF THE PEIERLS MECHANISM

Canadian Journal of Physics ◽

10.1139/p67-073 ◽

1967 ◽

Vol 45 (2) ◽

pp. 983-1016 ◽

Cited By ~ 248

Author(s):

Pierre Guyot ◽

John E. Dorn

Keyword(s):

Activation Volume ◽

Prismatic Slip ◽

Thermally Activated ◽

Covalently Bonded ◽

Higher Temperature ◽

Fe Alloys ◽

Increasing Temperature ◽

Peierls Model ◽

Volume Stress ◽

Good Agreement

A thorough review is made of the application of the Peierls model to the macroscopic plastic deformation of ionic crystals, metals, alloys, and covalently bonded crystals. The effects of the shape of the Peierls hill, kink–kink energies, and the frequency terms on the stress–temperature and activation volume–stress relationships are extended and discussed. Theory is compared with experimental results, giving special emphasis to recent advances. Single-crystal data for [Formula: see text] {110} thermally activated slip in Ta and Mo at low temperatures agree well with the dictates of the Peierls mechanism. Deformation characteristics of polycrystalline Fe alloys containing either 2 wt.% Mn or 11 at.% Mo agree with expectations based on the Peierls mechanism only at temperatures below about 200 °K. At higher temperatures, the effective stress decreases more slowly and the activation volume increases more rapidly with increasing temperature than can be accounted for by the Peierls mechanism. Over this higher temperature range, however, the experimental data are in good agreement with Escaig's mechanism based on the recombination of dissociated screw dislocations. It is also shown that low-temperature [Formula: see text] {123} slip in AgMg, prismatic slip in Ag plus 33 at.% Al, and in Mg plus 6–12 at.% Li occurs by the Peierls mechanism.

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A New Defect in Polyethylene Single Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070795 ◽

1973 ◽

Vol 31 ◽

pp. 70-71

Author(s):

E. L. Thomas ◽

S. L. Sass

Keyword(s):

Single Crystals ◽

Screw Dislocation ◽

Small Distance ◽

Dipole Model ◽

Dislocation Dipole ◽

Chain Folding ◽

Black And White ◽

Polymer Crystal ◽

Different Types

In polyethylene single crystals pairs of black and white lines spaced 700-3,000Å apart, parallel to the [100] and [010] directions, have been identified as microsector boundaries. A microsector is formed when the plane of chain folding changes over a small distance within a polymer crystal. In order for the different types of folds to accommodate at the boundary between the 2 fold domains, a staggering along the chain direction and a rotation of the chains in the plane of the boundary occurs. The black-white contrast from a microsector boundary can be explained in terms of these chain rotations. We demonstrate that microsectors can terminate within the crystal and interpret the observed terminal strain contrast in terms of a screw dislocation dipole model.

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Dislocations in alumina deformed by prismatic slip

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110179 ◽

1978 ◽

Vol 36 (1) ◽

pp. 606-607

Author(s):

J. Cadoz ◽

J. Castaing ◽

J. Philibert

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Basal Slip ◽

Prismatic Slip ◽

Compression Tests ◽

Thin Sections ◽

Burgers Vector ◽

Maximum Deformation ◽

Transmission Electron ◽

Mechanical Thinning

Plastic deformation of alumina has been much studied; basal slip occurs and dislocation structures have been investigated by transmission electron microscopy (T.E.M.) (1). Non basal slip has been observed (2); the prismatic glide system <1010> {1210} has been obtained by compression tests between 1400°C and 1800°C (3). Dislocations with <0110> burgers vector were identified using a 100 kV microscope(4).We describe the dislocation structures after prismatic slip, using high voltage T.E.M. which gives much information.Compression tests were performed at constant strainrate (∿10-4s-1); the maximum deformation reached was 0.03. Thin sections were cut from specimens deformed at 1450°C, either parallel to the glide plane or perpendicular to the glide direction. After mechanical thinning, foils were produced by ion bombardment. Details on experimental techniques can be obtained through reference (3).

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