Abstract
Understanding radiation performance of nanocrystalline Zr-based alloys is essential to develop internal components and external cladding materials with self-healing capabilities for longer and safer life cycles in harsh reactor environments. However, the precise role of interfaces in modifying defect production and evolution in α-Zr is not yet determined. Using atomistic simulation methods, we investigate the influence of different atomic grain boundaries (GBs) in thermodynamic and kinetic properties of defects on short timescales. We observe that the sink efficiency and sink strength of interfaces vary significantly with the boundary structures, with a preference to absorb interstitials (vacancies) when the GBs are semi-parallel (semi-perpendicular) relative to the basal planes. Further, we identify three distinct primary cascade geometries, and find that the residual defect clustering in grain interiors depends on how the atomic GBs modify the spatial distribution of defects within the crystal structure. Finally, we explain and discuss the dynamic results in terms of energetic and kinetic behaviors of defects near the pristine and damaged boundaries. Eventually, these will provide a microscopic reference for further improving the radiation response of Zr by using fine grains or by introducing a high density of dispersoids in material metallurgy.
Highlights
We investigate the influence of different atomic grain boundaries (GBs) on energetic, thermodynamic and kinetic properties of radiation-produced defects in hcp Zr, using molecular statics (MS), molecular dynamics (MD) and the climbing image-nudged elastic band method
Using MD, we investigated the evolution of the collision cascades on ps timescale, and analyzed changes in the number of surviving defects, as well as the structure of residual defect clusters in the grain interiors, as a function of GB type and initial distance of the PKA from the GB plane
Considering the kinetic interaction width and the decrease in the defect migration barriers, we find that the twist structures facilitate the diffusion of self-interstitial atoms (SIA) toward the GB plane with a barrier of 0.007 eV, while the vacancies will be immobile in the region close to the boundary due to their higher migration barriers (~0.16 eV) and activation temperatures (~1856.7 K), leading to an interstitial-saturated GB surrounded by excess vacancies in the bulk region, consistent with MD simulations
Summary
In the case of hexagonal close-packed (hcp) materials, Yao[45] investigated dynamics of defects in hcp Ti, and reported that the GBs act as sinks of radiation-produced point defects, with efficiency depending on the degree of overlap between the GB and the cascade damage region. Woo in the theory of irradiation deformation in non-cubic metals[47], reported that SIAs had a higher mobility in the basal plane than along the < c> axis in hcp Zr and that the vacancies had semi-isotropic diffusional behavior He concluded that the GBs perpendicular to the basal plane absorbed more interstitial atoms, while GBs parallel to the basal plane absorbed more vacancies[47]. These will provide a microscopic reference for further improving the radiation performance of Zr by using fine grains or by introducing a high density of dispersoids
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call