The behavior of a dislocation in the vicinity of an interface between 2 half-crystals with markedly different elastic moduli was investigated. The half-crystals had a body-centered cubic structure with the same orientations and lattice parameters and were welded along the (100) plane; parallel to the a[001] screw dislocation. Two interatomic potentials which represented a-Fe were used. A detailed exploration of the Peierls valleys within 4a of the interface was performed by applying an external stress which balanced the local lattice friction and the long-range image force. It was found that the mean stresses of each valley agreed approximately with stress curves which were determined on the basis of a continuous Peierls dislocation core, as perturbed by the interface. However, the simulation exhibited a stress peak which was lower and more extended. Changes in the dislocation core were observed as the dislocation approached the interface. In the soft medium, the core tended to become slightly narrower, while it clearly widened in the hard medium. This was because the effect of the applied stress was uniform throughout each half-crystal, whereas the image force was stronger on those parts of the dislocation core which were closer to the interface. Systematic variations in the Peierls-valley amplitudes were found. When the interface was approached from the soft-medium side, the amplitude increased. It decreased upon approaching from the hard side. The latter decrease was such that the Peierls valleys completely disappeared near to the interface, and an unstable zone formed on the hard side. It was possible to keep dislocations there, but only in a dissociated form that comprised 2 partials with b/2 screw components. The stacking fault that was created, which was not normally stable in the body-centered cubic structure, was of so-called unstable-fault type.

Atomistic Computation of the Image Force on a Dislocation in a Bicrystal II: Case of a Large Difference between the Elastic Moduli of the Two Half-Crystals. P.Beauchamp, J.Lépinoux: Philosophical Magazine A, 1998, 77[3], 541-60