Tem of Climb-Dissociated Dislocations in Sapphire

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100055011 ◽

1982 ◽

Vol 40 ◽

pp. 554-555

Author(s):

K.P.D Lagerlof ◽

T.E. Mitchell ◽

A.H. Heuer

Keyword(s):

Basal Slip ◽

Break Up ◽

Diffusive Processes ◽

Edge Dislocations

1. Introduction. Dislocation dipoles consisting of perfect edge dislocations are formed during basal slip in sapphire. These dipoles are unstable and break up by several diffusive processes;

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Mobility of Edge Dislocations in the Basal‐Slip System of Zinc

Journal of Applied Physics ◽

10.1063/1.1709058 ◽

1967 ◽

Vol 38 (10) ◽

pp. 4011-4018 ◽

Cited By ~ 54

Author(s):

D. P. Pope ◽

T. Vreeland ◽

D. S. Wood

Keyword(s):

Slip System ◽

Basal Slip ◽

Edge Dislocations

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Dislocation Dipole Annihilation in Pure Sapphire (Al2O3)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100097739 ◽

1981 ◽

Vol 39 ◽

pp. 232-233

Author(s):

K.P.D. Lagerlöf

Keyword(s):

Plastic Deformation ◽

Quantitative Analysis ◽

Plastic Strain ◽

Basal Slip ◽

Bulk Diffusion ◽

Diffusion Kinetics ◽

Dislocation Dipole ◽

Pipe Diffusion ◽

Diffusive Processes ◽

Kinetics Of

Dislocation dipoles are often formed during deformation of sapphire (Al2O3) undergoing basal slip by edge-trapping of 1/3<1120> dislocations. Tne dipole concentration remains constant with increasing plastic deformation because the formation of new dipoles due to increasing plastic strain is offset by dipole annihilation by diffusive processes. Dipole annihilation in sapphire occurs in five distinguishable steps:(1) the dipole width fluctuates by self-climb, forming narrower and wider segments; (2) narrow segments transform into faulted dipoles by self-climb; (3) both perfect and faulted dipoles pinch off to form prismatic loops, primarily by self-climb; (4) faulted loops and dipoles rotate into edge orientation; and (5) loops grow or annihilate by climb. The kinetics of dipole annihilation thus depends on both self-climb and climb, that is, on both pipe-diffusion and bulk-diffusion kinetics, and so quantitative analysis of these changes during annealing will give valuable information on diffusion in sapphire. The objective of this paper is to present a brief qualitative analysis of the kinetics of dislocation dipole annihilation in pure sapphire.

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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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