Irradiation-induced grain boundary facet motion: In situ observations and atomic-scale mechanisms

Abstract

Metals subjected to irradiation environments undergo microstructural evolution and concomitant degradation, yet the nanoscale mechanisms for such evolution remain elusive. Here, we combine in situ heavy ion irradiation, atomic resolution microscopy, and atomistic simulation to elucidate how radiation damage and interfacial defects interplay to control grain boundary (GB) motion. While classical notions of boundary evolution under irradiation rest on simple ideas of curvature-driven motion, the reality is far more complex. Focusing on an ion-irradiated Pt Σ3 GB, we show how this boundary evolves by the motion of 120° facet junctions separating nanoscale {112} facets. Our analysis considers the short- and mid-range ion interactions, which roughen the facets and induce local motion, and longer-range interactions associated with interfacial disconnections, which accommodate the intergranular misorientation. We suggest how climb of these disconnections could drive coordinated facet junction motion. These findings emphasize that both local and longer-range, collective interactions are important to understanding irradiation-induced interfacial evolution.

Linking simulated polycrystalline thin film microstructures to physical vapor deposition conditions

“…However, the termination of grain boundaries at the film-vapor interface, together with the dynamics of the interface itself, dictates both the formation of surface roughness and the overgrowth phenomenon described above. One consequence of the relative immobility of grain boundaries is the emergence of alternating kinks and facets in a subset of grain boundaries [56]. This behavior appears to arise because of the competition between abutting grains with similar, mirrored misorientation, i.e., 0…”

Complex dislocation loop networks as natural extensions of the sink efficiency of saturated grain boundaries in irradiated metals

“…DZs are the microstructural manifestation of highly complex defect-GB interactions. Broadly speaking, these interactions relate the overall GB character, defined by the five-dimensional (5D) space consisting of misorientation and inclination degrees of freedom (dof), with the structure and properties of irradiation defect clusters, although extensive studies in recent times culminating in previously unidentified findings and a much improved understanding of the internal structure of GBs are fast changing this picture (6,(16)(17)(18)(19). In a previous work (20), we have shown that the evolution of the width of the DZ with irradiation dose is associated with changes in GB (internal) microstates.…”

Thermal and Radiation Stability in Nanocrystalline Cu

“…Liu et al were the first to suggest thermal spike diffusion phenomenon [ 50 ]. If the thermal spike occurs on or near a grain boundary, the atoms are thermally activated and can jump across the boundary [ 32 , 57 , 58 , 59 ], resulting in grain boundary migration and thus grain growth.…”