Binary effect of He and H on the intra- and inter-granular embrittlement in Fe

Tian, Zhixue; Xiao, Wei; Wan, F.R.

doi:10.1016/j.jnucmat.2010.10.016

Cited by 22 publications

(10 citation statements)

References 30 publications

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“…It is now well recognized that a single He in bcc metals such as Fe, Mo, W, V, Nb, Ta will occupy a TIS. 24 The electron density at TIS is lower than OIS in bcc 6 crystals, although its volume is smaller the latter. A TIS in bcc lattice has four nearest neighbors at a distance of 0.559a (a is the lattice constant) while an OIS has two nearest neighbors at a distance of 0.5a and four next-nearest-neighbors at 0.707a.…”

Section: A Positioning and Migration Of A Single Interstitial Hementioning

confidence: 96%

Migration of helium-pair in metals

Cao

2016

Journal of Nuclear Materials

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Understanding helium accumulation in plasma-facing or structural materials in a fusion reactor starts from uncovering the details of the migration of single and paired He interstitials. We have carried out a first-principles density functional theory investigation into the migration of both a single interstitial He atom and an interstitial He-pair in bcc (Fe, Mo and W) and fcc (Cu, Pd and Pt) metals. By identifying the most stable configurations of an interstitial He-pair in each metal and decomposing its motion into rotational, translational, and rotational-translational routines, we are able to determine its migration barrier and trajectory. Our first-principles calculations reveal that the migration trajectories and barriers are determined predominantly by the relatively stable He-pair configurations which depend mainly on the stability of a single He in different interstices. Contrary to atomistic studies reported in literature, the migration barrier in bcc Fe, Mo, and W is 0.07, 0.07, and 0.08 eV respectively, always slightly higher than for a single interstitial He (0.06 eV for all three). Configurations of a He-pair in fcc metals are much more complicated, due to the stability closeness of different interstitial sites for a single He atom. In both Cu and Pd, the migration of a He-pair proceeds by moving one He at a time from one tetrahedral site to neighboring octahedral site; whereas in Pt the two He move simultaneously because the bridge interstitial site presents an extremely low barrier. The migration barrier for a He-pair is 0.05, 0.15, and 0.04 eV for Cu, Pd, and Pt, slightly lower than (in Cu), or similar to (in Pd and Pt) a single He, which is 0.08, 0.15, and 0.03 eV, respectively. The associative motions of a He-pair are ensured by the strong He-He interactions in metals which are chemical bonding-like and can be described very well with Morse potentials.Comment: 34 pages, 12 figure

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Section: A Positioning and Migration Of A Single Interstitial Hementioning

confidence: 96%

Migration of helium-pair in metals

Cao

2016

Journal of Nuclear Materials

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“…We find the planar rhombus structure is the lowest-energy isomer for Cu 4 cluster, different from the three-dimensional tetrahedron obtained by Seko using the same computation method. 21 The reason for such a discrepancy is not clear to us. One might expect from simple bond-counting argument: the both clusters have the same number of 1nn Fe-Cu bonds, but the 3D cluster has less 2nn Fe-Cu bonds.…”

Section: Pure Cu Clustersmentioning

confidence: 93%

“…7 Atomistic simulation techniques have proven to be an alternative tool to study the interaction of solute atoms with irradiation-produced point defects such as vacancies, SIAs, H, and He in bcc Fe. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Extensive studies on ferritic steels used in manufacture reactor pressure vessels (RPVs) have demonstrated that Curich clusters or precipitates intensify embrittlement. Arokiam et al [8][9][10][11] found by MD simulations that Cu precipitates in iron can be sinks for both vacancy and interstitial defects, and can act as strong recombination centers under irradiation conditions.…”

Section: Introductionmentioning

confidence: 99%

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Interaction of He with Cu, V, and Ta in bcc Fe: A first-principles study

Yan¹,

Tian²,

Xiao³

et al. 2011

Journal of Applied Physics

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Precipitates often play key roles in improving the mechanical performance of structural materials. Using first-principles density functional theory method, we have calculated the geometry and energetics of small X n and X n He (X ¼ Cu, V, and Ta) clusters in bcc Fe matrix to investigate the effect of He on X precipitation on the initial stage in neutron-irradiated Fe alloys. Both substitutional and interstitial He attract solute atoms. The attraction of a substitutional He and a Cu atom is as strong as 0.30 eV (nearest neighbor) or 0.25 eV (next-nearest neighbor), even stronger than the vacancy-Cu pair. Such an attraction facilitates the clustering of Cu atoms. By comparison, the attraction of He to V (0.02 eV) or Ta (0.22 eV) is weaker than that of a vacancy. We find that one He can bind up to four Ta atoms to form a tetrahedron, despite the fact that in the absence of He, Ta atoms prefer to stay away from each other. The effect of He on the solute-solute and solute-matrix interactions can be understood from the facts that He behaves both as a free-volume filler and as a bonding insulator.

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“…[6][7][8][9][10][11][12][13] The segregation effect of Co and Cr on bcc Fe S3[110] (111) GB cohesion were investigated by the DMol method. The results indicated that the segregation of Cr could improve GB cohesion.…”

Section: Introductionmentioning

confidence: 99%

First principles investigation into effects of Cr on segregation of S or Cl at α-Fe Σ5(210) grain boundary

Dang

Wang

et al. 2014

Materials Research Innovations

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In this paper, the effects of Cr on segregation of S or Cl atoms at the a-Fe S5(210) grain boundary (GB) are studied using a first principles method, CASTEP. In the absence of Cr, S can be trapped at the interstitial site of the Fe GB. Cl is not apt to be segregated at the GB. The presence of Cr acts as an enhancer, and can alleviate the detrimental effect of Cl and S. Furthermore, increasing the Cr content has a more effective impact on Cl. Based on the segregation energy analysis, it is also found that Cr can effectively prohibit S from segregating to the GB and therefore eliminate the embrittlement of the GB induced by S; however, it has little effect on Cl. Cr prevents the expansion of interfacial bonds Fe-Fe or Fe-S/Cl for S, and Cl segregating in Fe GB even exhibited shorter bond lengths with increasing Cr content. Therefore, Cr alleviates embrittlement or corrosion effect of S and Cl in Fe GB. Analysis of densities of states further indicates that Cr should alleviate the detrimental effect of S and Cl, enhancing the cohesion of a-Fe GB.

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Binary effect of He and H on the intra- and inter-granular embrittlement in Fe

Cited by 22 publications

References 30 publications

Migration of helium-pair in metals

Migration of helium-pair in metals

Interaction of He with Cu, V, and Ta in bcc Fe: A first-principles study

First principles investigation into effects of Cr on segregation of S or Cl at α-Fe Σ5(210) grain boundary

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