In the present work, a particular case of constrained dislocation glide that was typical of deformation in small volumes as, for example, in thin films was studied. The specific problem addressed concerns the glide and interaction of 2 unlike screw dislocations bowing out in constrained channels on parallel glide planes. The situation described corresponds not only to thin film deformation but also to the constrained glide of dislocations in the channels between the dislocation walls in persistent slip bands in fatigued metals. The main objective of the study was to determine the flow stress and to assess in an analytic approximation how the contributions of the dipolar interaction stress and of the bowing stress which both vary in space superimpose. It was argued that the dipolar interaction between the two dislocations was overcome by ‘bowing-out’ and not by separation of the aligned dislocation dipole ‘at constant shape’. A general conclusion of the numerical analysis was that, aside from one trivial irrelevant case, the resulting flow stress was never a simple linear sum of the Orowan bowing stress and the dipole passing stress. Rather, the flow stress was always governed by the stronger of the two interactions and is, typically, at most about 20% larger than either the Orowan stress or the dipole passing stress, depending on which of the two was larger. The numerical results were discussed briefly with respect to an idealized example of dislocation glide in thin films and in more detail with regard to dislocation glide in the channels of persistent slip bands. In the latter case, the present results match nicely with the interpretation of the cyclic flow stress of persistent slip bands in terms of the so-called composite model which considers explicitly the weighted contributions of the local flow stresses in the relatively soft channels and in the harder dislocation walls to the overall stress.

Constrained Glide and Interaction of Bowed-Out Screw Dislocations in Confined Channels. H.Mughrabi, F.Pschenitzka: Philosophical Magazine, 2005, 85[26-27], 3029-45