Interaction of Lomer–Cottrell locks with screw dislocations

Abstract

In fcc crystals, dislocations are dissociated into partial dislocations and, therefore, restricted to move on {111} glide planes. By junction reactions with dislocations on two intersecting {111} planes, Lomer–Cottrell dislocations along ⟨110⟩ directions can be formed which are barriers for approaching screw dislocations. Treating the interaction between a dissociated screw dislocation and a LC lock conventionally, using classical continuum theory and assuming the partials to be Volterra dislocations, leads to erroneous conclusions. A realistic result can only be obtained in the framework of the Peierls model, treating the partials as Peierls dislocations and explicitly taking account of the change in atomic misfit energy in the glide plane. At even moderate stresses (at less than 3 × 10⁻³ µ in Cu), the screw will combine with the LC lock to form a Hirth lock. As a result, the nature of the repulsive force will change drastically.

Keywords:

• dislocation interaction
• dislocation structure
• Lomer–Cotrell dislocations
• Peierls model