Interface dislocation patterns and dislocation nucleation in face-centered-cubic and body-centered-cubic bicrystal interfaces

Nanolayered metallic composites exhibit unusual high strength at the layer thickness in nanometers. Plastic deformation including nucleation, glide, and transmission of dislocations is strongly related to interface structure and properties. Combining atomistic simulations with the classical Frank-Bilby theory, we studied dislocation structures of semi-coherent interfaces between face-centered-cubic (fcc) and body-centered-cubic (bcc) crystals. An atomically informed Frank-Bilby theory is proposed for quantitative analysis of interface dislocations. The results showed that (1) seven sets of interface dislocations are present in the Nishiyama-Wasserman (NW) interface and two sets of interface dislocation in the Kurdjumov-Sachs (KS) interface although they are misoriented by only ∼5.6; (2) Burgers vectors of interface dislocations can be well defined in a commensurate/coherent dichromatic pattern (CDP) lattice corresponding to the NW interface and the Rotation CDP (RCDP) lattice corresponding to the KS interface; (3) the CDP and RCDP lattices are not simply a geometric average of the two natural lattices; finally we demonstrated that (4) the nucleation of dislocations, including interface dislocation loops corresponding to interface sliding and lattice dislocation loops corresponding to plastic deformation in crystals, are strongly correlated with interface dislocation patterns.