Abstract
By using a generalized, spatially resolved rate theory, we systematically studied the irradiation-induced diffusion and segregation of point defects near triple junctions. Our model captured not only the formation, growth, and recombination of point defects but also the interaction of these defects with pre-existing defects. We coupled the stress field of the triple junction with defect diffusion via a modified chemical potential. The residual stress fields of grain boundaries and triple junctions are modeled via disclination mechanics theory. By assessing the behavior of 144 triple junctions with vacancy and interstitial defects, we correlated defect-sink efficiencies with key characteristics of triple junctions. For vacancies, the geometric configuration of triple junctions dominated sink efficiency, suggesting that equiaxed grains would resist the accumulation of vacancies more than elongated grains. For interstitials, the sink density of the grain boundaries composing the triple junctions dominated sink efficiency. Hence, the interstitial concentration may be managed by adjusting the structure of the grain boundaries. Overall, we illustrated the complex coupling between pre-existing defects and radiation-induced defects through interaction of their stress fields. This theoretical framework provides an efficient tool to rapidly assess defect management in microstructures.
Highlights
The ability of a material to manage and eliminate point defects, i.e., interstitials and vacancies, plays a significant role in determining how its mechanical properties will be affected by irradiation over extended periods of time
Some residual defects remain, leading to the growth of point-defect clusters. These point defects and their associated clusters eventually diffuse toward different types of pre-existing microstructural sinks, which include dislocation loops, grain boundaries (GBs), and triple junctions (TJs)
While the proposed framework simplifies microstructural configurations and the complexity of pre-existing defects, it is an efficient tool to rapidly assess defect managements in microstructures that correlates with experimental observations
Summary
The ability of a material to manage and eliminate point defects, i.e., interstitials and vacancies, plays a significant role in determining how its mechanical properties will be affected by irradiation over extended periods of time. Harkness and Li [2] studied void formation in 304 stainless steel and suggested that increasing the presence of various microstructural sink types would increase resistance to damage. Following up on this hypothesis, Singh [3] further studied the relationship between grain size and void swelling, finding that smaller grains did reduce radiation damage, likely due to the increased density of GB sinks. Han et al [5] observed that the density and size of cavities were reduced in nanograined Cu as compared to coarse-grained Cu when subjected to He irradiation. Alsabbagh et al [6] observed a reduction in radiation-induced hardening and embrittlement in ultra-fine-grained steel as compared to coarse-grained steel, while Sun et al [7] quantified the reduction in swelling and swelling rate in 304 L stainless steel when using an ultra-fine-grained structure
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