Glide and Climb

Kinetics of Materials. By Robert W. Balluffi, Samuel M. Allen, and W. Craig Carter. 253 Copyright 2005 John Wiley Sons, Inc. 

1Provided that the Peierls force is not too large (see Section 11.3.1). 

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Figure 11.1 Glide and climb of edge dislocation in primitive cubic crystal (b = [600],...

In a more general stress field, the force (which is always perpendicular to the dislocation line) can have a component in the glide plane of the dislocation as well as a component normal to the glide plane. In such a case, the overall force will tend to produce both glide and climb. However, if the temperature is low enough that no significant diffusion is possible, only glide will occur. 

Thermally Activated Motion of Sharp Interfaces by Glide and Climb of Interfacial Dislocations... 

The motion of many interfaces requires the combined glide and climb of interfacial dislocations. However, this can take place only at elevated temperatures where sufficient thermal activation for climb is available. 

The example in Fig. 13.4 is an extension of the model for the motion of a small-angle boundary by the glide and climb of interfacial dislocations (Fig. 13.3). Figure 13.4 presents an expanded view of the internal surfaces of the two crystals that face each other across a large-angle grain boundary. Crystal dislocations have... 

Fig. 21. A bent crystal, as in (a), will become polygonal either by glide alone, as in (b) or as a result of glide and climb, as in (c).

Section II,C,1) dislocations may climb, and the polygonal walls are produced by a combination of both glide and climb. It is important to note that the direction of the arrays of emergent dislocations in polygonal walls is perpendicular to the trace of the glide planes. This fact is also (along with the directions of pileups mentioned earlier) used to deduce the nature of the dislocations present in a crystal. 

In this mechanism creep occurs by dislocation motion, i.e., glide and climb. For the climb-controlled process the creep rate can be expressed as... 

Figure 17.4a Reprinted with permission from Gilman, J.J. and Johnston, W.G. (1956) Observations of dislocation glide and climb in lithium fluoride crystals , J. Appl. Phys. 27, 1018. Copyright 1956, American Institute of Physics.

The Homstra dissociation into collinear half-partials [Eq. (6)] is commonly observed, most often by climb. However, evidence has been found for combinations of glide and climb dissociation on both rational and irrational planes. The 100 fault plane predominates, regardless of stoichiometry, followed by 110, 112, 113, and 111 [26]. Occasionally, pure glide dissociation is observed, for example, of screw dislocations on the 110 plane of stoichiometric crystals [26]. Although faults in spinel exhibit a dear preference for the 100 plane and other low-index planes, they are also observed to be wavy and to lie on irrational planes (see Figure 9.20). 

Fig. 3.72 Dislocations in MgAl204 spinel deformed at 1800 °C, a 2 % strain, showing mostly edge dislocations and dipoles produced by glide, and b 3 % strain, showing uniform 3-dimensional network of dislocations produced by glide and climb [38]. With kind permission of John Wiley and Sons...

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