Irradiation deformation near different atomic grain boundaries in α-Zr: An investigation of thermodynamics and kinetics of point defects

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.

Primary damage production in the presence of extended defects and growth of vacancy-type dislocation loops in hcp zirconium

“…Similarly, vacancies preferentially form near grain boundaries in Zr [65] and in cubic materials [78,79]. As observed by Harte et al [80] and in other experimental studies [5,81], a-type loops are randomly distributed at lower irradiation doses, and loops' separation distances are relatively large.…”

“…In the previous section, it was observed that GBs promote vacancy supersaturation by acting as a cascade sink. However, this result might depend on the grain boundary orientation [32,65,66]. Here, by combining classical diffusion sink arguments, MD simulations of dislocation loop stability and experimental evidence, vacancy supersaturation near GB is established in a definitive manner.…”

“…However, this relation has not been systematically studied. In addition, different types of GBs may produce different levels of strain field that would then affect their sink strength as suggested in [32,65]. In the future, studying these factors would be of interest.…”

Trapping Capability of Small Vacancy Clusters in the α-Zr Doped with Alloying Elements: A First-Principles Study

“…A large number of point defects in zirconium alloys under a fast neutron flux are created, such as vacancies and self-interstitials. These point defects can then evolve to small defect clusters, which significantly influence the in-pile performance of zirconium alloys [4][5][6]. Alternatively, the stability of smallvacancy clusters in zirconium has been investigated using first-principle calculations [7].…”

In Situ TEM Study of Microstructure Evolution of Zr-Nb-Fe Alloy Irradiated by 800 keV Kr2+ Ions

“…In the past several decades, the irradiation behaviors of zirconium alloys have been widely investigated [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. The main investigations conducted so far including the following: (i) phase changes, nanocrystallization, and amorphization [ 5 , 6 ]; (ii) particle dissolution or precipitation [ 7 ]; (iii) the effect of chemical composition and preparation technology on the irradiation behaviors [ 8 , 9 ]; (iv) helium behaviors in zirconium alloys [ 10 ]; (v) dislocation formation and characteristic [ 11 ]; (vi) post-irradiation corrosion behaviors [ 12 ]; (vii) computer simulation such as molecular dynamics for irradiation behaviors [ 13 ]. In addition, the microhardness obtained by nanoindenter is an important method for characterizing the mechanical properties before and after ion irradiation because of the limited irradiation depth.…”