The behavior of a dislocation in the vicinity of an interface between 2 half-crystals with markedly different elastic moduli was investigated via computer simulation. The 2 half-crystals had body-centered cubic structures of the same orientation and lattice parameter, and were welded along the (100) plane; parallel to an a0[001] screw dislocation. Interatomic potentials for a-Fe were used. Detailed exploration of the Peierls valleys within 4a0 of the interface was performed by applying an external stress which balanced both the local lattice friction and the long-range image force. It was found that the mean stresses of each valley roughly followed a stress curve which had been determined on the basis of a continuous Peierls dislocation core; as perturbed by the interface. The simulated stress peak was lower and more extended. Changes in the dislocation core were observed as the dislocation approached the interface. In the softer half-crystal, the core tended to become slightly narrower. It clearly widened in the harder crystal. This was suggested to be because the effect of the applied stress was uniform throughout each half-crystal, whereas the image force acted more strongly on the parts of the dislocation core which were closer to the interface. Systematic variations in the Peierls-valley amplitudes were noted. When the interface was approached from the softer-crystal side, the amplitude increased; whereas it decreased during approaches from the hard-crystal side. The latter decrease was such that Peierls valleys completely disappeared near to the interface, and an unstable zone formed on the hard-crystal side. It was possible to retain the dislocations there, but only in a dissociated form that comprised 2 partials with b/2 screw components. The created stacking fault, which was not normally stable in the body-centered cubic structure, was of the so-called unstable-fault type which had been suggested to play a key role in dislocation nucleation at crack tips.

Atomistic Computation of the Image Force on a Dislocation in a Bi-Crystal - 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