Alex Selimov

Lattice dislocation induced misfit dislocation evolution in semi-coherent {111} bimetal interfaces
Authors: Alex Selimov, Shuozhi Xu, Kevin Chu, and David L. McDowell

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Characterization of misfit dislocation evolution in bimetal interfaces is critical for understanding plasticity in nanolaminates as local misfit dislocation structures affect dislocation/interface interactions. This work utilizes the Concurrent Atomistic- Continuum method to probe the evolution of misfit structures at semi-coherent Ni/Cu and Cu/Ag interfaces impinged by dislocation pileups generated via nanoindentation. A continuum microrotation metric is computed and used to visualize the evolution of the interface misfit dislocation pattern. The stress state from approaching dislocations induces mixed contraction and expansion of misfit dislocation structures. A lower misfit dislocation density coincides with greater localized deformation for atoms near misfit nodes for Ni/Cu. The increased misfit dislocation density for Cu/Ag alternatively distributes the deformation over a larger percentage of atoms at the interface. Interface sliding is found to facilitate deformation extending into the bulk lattices centered on misfit nodes. The depth of penetration of those fields is greater for Ni/Cu than for Cu/Ag.

Figure 8: a) Atom (red) and finite element node(blue) representation of model with overlaid schematics of boundary conditions and CAC finite element shapes. b) Common neighbor analysis of relaxed Ni/Cu interface and c) common neighbor analysis of relaxed Cu/Ag interface. Green atoms are FCC, red atoms are HCP, blue atoms are BCC, and gray atoms are others. Insets represent zoomed in sections of interfaces capturing misfit nodes. Misfit node spacings of 9.5 nm and 2.2 nm agree with values from the literature