A molecular dynamics study of helium diffusion and clustering in fcc nickel

Wang, Chengbin; Ren, Chao; Zhang, Wei; Gong, Hengfeng; Huai, Ping; Zhang, Zhu; Deng, Hui; Hu, Wangyu

doi:10.1016/j.commatsci.2015.05.017

Cited by 20 publications

(6 citation statements)

References 25 publications

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“…A variable temperature molecular dynamics study of helium diffusion and clustering in Ni confirmed the creation and annihilation of Frenkel pairs and complex formation at 425 • C, with defect production, migration, and cluster growth accelerating at higher temperatures. However, at temperatures at or below ≈325 • C, defect production was hampered resulting in a higher density of smaller defect clusters [36]. However, helium-vacancy complexes are believed to be immobile in the case of the 300 • C implantation in Fe; applying the same reasoning to the current work, one would expect the bubble density to be higher for the NC Ni sample compared to Fe, yet the results are contradictory to this assumption.…”

Section: Resultsmentioning

confidence: 55%

“…The helium implantation profiles shown in Figure 1 show negligible ion beam transmission through the sample, and an area between ≈10 and 30 nm in depth with high overlap between the ion implantation density and the defect production density. This is expected to lead to favorable helium-vacancy bubble formation, although the portion of helium in the crystal is the result of a process where sinks compete to trap helium according to a set of energetics that controls the kinetics of helium transport and its ultimate fate [19,36].…”

Section: Resultsmentioning

confidence: 99%

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Implications of Microstructure in Helium-Implanted Nanocrystalline Metals

et al. 2022

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Helium bubbles are known to form in nuclear reactor structural components when displacement damage occurs in conjunction with helium exposure and/or transmutation. If left unchecked, bubble production can cause swelling, blistering, and embrittlement, all of which substantially degrade materials and—moreover—diminish mechanical properties. On the mission to produce more robust materials, nanocrystalline (NC) metals show great potential and are postulated to exhibit superior radiation resistance due to their high defect and particle sink densities; however, much is still unknown about the mechanisms of defect evolution in these systems under extreme conditions. Here, the performances of NC nickel (Ni) and iron (Fe) are investigated under helium bombardment via transmission electron microscopy (TEM). Bubble density statistics are measured as a function of grain size in specimens implanted under similar conditions. While the overall trends revealed an increase in bubble density up to saturation in both samples, bubble density in Fe was over 300% greater than in Ni. To interrogate the kinetics of helium diffusion and trapping, a rate theory model is developed that substantiates that helium is more readily captured within grains in helium-vacancy complexes in NC Fe, whereas helium is more prone to traversing the grain matrices and migrating to GBs in NC Ni. Our results suggest that (1) grain boundaries can affect bubble swelling in grain matrices significantly and can have a dominant effect over crystal structure, and (2) an NC-Ni-based material can yield superior resistance to irradiation-induced bubble growth compared to an NC-Fe-based material and exhibits high potential for use in extreme environments where swelling due to He bubble formation is of significant concern.

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Section: Resultsmentioning

confidence: 55%

Section: Resultsmentioning

confidence: 99%

Implications of Microstructure in Helium-Implanted Nanocrystalline Metals

et al. 2022

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“…The nucleation of cavities can be driven by the accumulation of either helium atoms or vacancies. At 320 °C, vacancies do not have significant thermal mobility in nickel [42], whereas helium is very mobile [43], likely making nucleation driven by helium accumulation. Once enough helium pressure builds in the cavity to stabilize it against the surface energy of the nickel lattice, the cavity, now termed a bubble, can grow through the slow accumulation of additional vacancies until it reaches a critical size at which grow is unhindered [44].…”

Section: Results Of Microstructure Characterizationmentioning

confidence: 99%

Report on Evolution of Inconel 718 Following HFIR Irradiation

Taller¹,

Coq²,

Massey³

et al. 2022

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“…Similar behavior has been observed before. [14] Owing to thermal diffusion and a longer irradiation time in sample S 2 , the helium atoms are capable of diffusing into the deeper matrix, [27] resulting in the aforementioned deviation. In this work, a comparison between the NiMo (NP) and Hastelloy N alloys, focusing on helium-induced damage, was conducted to reveal the irradiation resistance of the former.…”

Section: Resultsmentioning

confidence: 99%

Helium bubble formation and evolution in NiMo-Y₂O₃ alloy under He ion irradiation

et al. 2022

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We report helium ion irradiation experiments for a new type of dispersion-strengthened NiMo-Y2O3 alloy with three different irradiation doses and varying irradiation dose rates at 750 °C to evaluate its helium-induced damage behavior. Transmission electron microscopy was used to reveal the evolution of helium bubbles after irradiation. The experimental results show that with increasing ion dose, the number density of helium bubbles increases continuously. However, the mean size of helium bubbles first increases and then decreases, mainly due to the varied ion dose rates. The volume fractions of helium bubbles in the three investigated samples after irradiation are 0.15%, 0.32%, and 0.27%, which are lower than that of the Hastelloy N alloy (0.58%) after similar irradiation conditions. This indicates that the NiMo-Y2O3 alloy exhibits better helium-induced-swelling resistance than the Hastelloy N alloy, highlighting its potential applicability to MSRs, from the perspective of irradiation performance.

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A molecular dynamics study of helium diffusion and clustering in fcc nickel

Cited by 20 publications

References 25 publications

Implications of Microstructure in Helium-Implanted Nanocrystalline Metals

Implications of Microstructure in Helium-Implanted Nanocrystalline Metals

Report on Evolution of Inconel 718 Following HFIR Irradiation

Helium bubble formation and evolution in NiMo-Y₂O₃ alloy under He ion irradiation

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A molecular dynamics study of helium diffusion and clustering in fcc nickel

Cited by 20 publications

References 25 publications

Implications of Microstructure in Helium-Implanted Nanocrystalline Metals

Implications of Microstructure in Helium-Implanted Nanocrystalline Metals

Report on Evolution of Inconel 718 Following HFIR Irradiation

Helium bubble formation and evolution in NiMo-Y2O3 alloy under He ion irradiation

Contact Info

Product

Resources

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Helium bubble formation and evolution in NiMo-Y₂O₃ alloy under He ion irradiation