Interface Structure and Radiation Damage Resistance in Cu-Nb Multilayer Nanocomposites

Abstract

We use atomistic simulations to show that upon removal or insertion of atoms, misfit dislocations in Cu-Nb interfaces shift between two adjacent planes, forming pairs of extended jogs. Different jog combinations give rise to interface structures with unlike densities but nearly degenerate energies, making Cu-Nb interfaces virtually inexhaustible sinks for radiation-induced point defects and catalysts for efficient Frenkel pair recombination.

High-strength and thermally stable bulk nanolayered composites due to twin-induced interfaces

“…Alloying 8 has been proposed to surmount the thermal stability problem. However, less attention has been paid to nanostructured multi-phase materials, which contain a higher density of heterophase interfaces than grain boundaries [9][10][11][12][13] . Of particular interest are composites comprised of two phases that do not chemically mix, leading to bimetal interfaces that are sharp and potentially ordered in atomic structure 14 .…”

Formation, migration, and clustering of delocalized vacancies and interstitials at a solid-state semicoherent interface

“…Some interfaces, such as coherent GBs, exhibit point defect behaviors not unlike those encountered in perfect crystals [6][7][8] . Point defects absorbed at some non-coherent interfaces, however, reconstruct into delocalized configurations that do not resemble conventional vacancies or interstitials [9][10][11][12][13] . The behavior of such configurations and their relation to properties such as diffusion are not intuitive 14 .…”

“…There may also be sites that do not support any point defects at all. When introduced at such sites, vacancies and interstitials spontaneously move to other nearby sites that do support compact or delocalized point defects [12][13][14] . The generalizable insights from these studies are qualitative: coherent regions of interfaces typically support compact point defects while delocalization is more likely at or near non-coherent ones.…”

“…We focus our attention on a single model system, namely a wellcharacterized heterophase interface found in magnetron sputtered Cu-Nb multilayer composites 13,15,16 and conclude that delocalized vacancies and interstitials at this interface do indeed form well-defined defects with definite atomic migration and clustering mechanisms. The complexity of these mechanisms is greater than that of conventional defects in crystalline materials, requiring different descriptions of defect reactions and modified expressions for migration rates.…”

“…While the structure of compact point defects is well understood, that of delocalized ones is not. Atomistic modeling has shown that interfacial point defect structures depend on interface structure and that they vary from location to location at individual interfaces: some interface sites may support compact point defects whereas others allow only for delocalized ones 13,33 . There may also be sites that do not support any point defects at all.…”