Forces on Dislocations in Multilayer Structures

Abstract

In multilayer structures, dislocation forces that arise from coherency strains are well understood in both the isotropic and anisotropic elastic cases. Image forces produced by elastic inhomogeneity have also been developed for single layers surrounded by extended phases. Image forces for the multilayers are shown to reduce to the simpler single embedded layer case to a good approximation. Image forces are shown to lead to a “stand-off” position of interface dislocations from the interface, with several implications for the properties of multilayer structures.

High-resolution electron microscopy of interfaces in fcc materials

“…As for the Nb/A1203 interface, the standoff distances observed in Ag/NiO and Au/NiO are also in agreement with the elastic model by Kamat et al. [41].…”

High resolution transmission electron microscopy studies of metal/ceramics interfaces

“…9). Note that most of these stand-off dislocations (Kamat et al, 1987(Kamat et al, , 1988Mader and Knauss, 1992) come in pairs with opposite characters, i.e., each pair forms a dipole. Figure 10 shows a Burgers circuit around one of the dislocations, which indicates that the projection of the Burgers vector is a/270118 where a is the lattice parameter of vanadium.…”

Atomic structure of heterophase interfaces

“…While in contrast to metal/metal systems, detailed atomic models of the misfit localization in metal/ceramic systems are not available at this point, HREM has nevertheless been very valuable for observing possible defect configurations. It has been shown first in the Nb/A1203 system that the tendency to produce coherency directly at the interface can be strong enough to have a stand-off distance for the misfit dislocation [9], which can be understood in terms of minimizing the elastic energy of the system [24]. The observations on Ag/NiO suggest that such a stand-off effect may also be typical fcr fcc metal/ceramic systems, lt is interesting to note that considerable variations in the atomic relaxations are possible even within the same system.…”