Atom probe tomography characterizations of high nickel, low copper surveillance RPV welds irradiated to high fluences

Miller, M.K.; Powers, Kathy A.; Nanstad, R.K.; Efsing, Pål

doi:10.1016/j.jnucmat.2013.01.312

Cited by 97 publications

(65 citation statements)

References 12 publications

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“…In support to our findings, P and Mn have been repeatedly observed to segregate on grain boundaries, dislocation lines, and loops [13,12,7]. Furthermore, all solutes considered here have been observed to form vacancy-solute clusters in model alloys and RPV steels [97,98,99], which is consistent with a positive coupling between solutes and point defects.…”

Section: Comparison With Experimental Ris Observationssupporting

confidence: 90%

“…The balance of the two effects provides an explanation for the experimentally-observed [46] existence of a switchover temperature between enrichment and depletion, and has been shown to be extremely sensitive to microstructure features (e.g., composition, strain fields, or sink density) [44,47]. On the contrary, no studies have yet fully uncovered the reasons for the systematic enrichment tendencies observed for the other solutes (Cu, Mn, Ni, P, Si) on grain boundaries, dislocations lines, and loops [46,12,13,7]. It is unclear whether this is due to vacancy drag, SIA transport, or a combination of both.The objective of this study is to perform an accurate analysis of SIA-driven solute transport in a set of dilute Fe-X alloys (X=Cr, Cu, Mn, Ni, P, Si), and provide a comprehensive overview of the expected intrinsic RIS behavior of said chemical species.…”

mentioning

confidence: 99%

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Solute diffusion by self-interstitial defects and radiation-induced segregation in ferritic Fe–X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

et al. 2020

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This work investigates solute transport due to self-interstitial defects and radiation induced segregation tendencies in dilute ferritic alloys, by computing the transport coefficients of each system based on ab initio calculations of binding energies and migration rates. The implementation of the self-consistent mean field method in the KineCluE code allows to extend the calculation of transport coefficients to arbitrary interaction ranges, crystal structures, and diffusion mechanisms. The results show that the diffusivity of P, Mn, and Cr solute atoms is dominated by the dumbbell mechanism, that of Cu by vacancies, while the two mechanisms might be in competition for Ni and Si, despite the fact that the corresponding mixed dumbbells are not stable. Systematic enrichment at defect sinks is expected for P and Mn solutes due to dumbbell diffusion, and for Si due mainly to vacancy drag. Vacancy drag is also responsible for Cu and Ni enrichment below 1085 K. The RIS behavior of Cr is the outcome of a fine balance between dumbbell enrichment and vacancy depletion. Therefore, for dilute Cr concentrations global enrichment occurs below 540 K, and depletion above. This threshold temperature grows with solute concentration. The findings are in agreement with experimental observations of RIS and clustering phenomena, and confirm that solutedefect kinetic coupling plays an important role in the formation of solute clusters in reactor pressure vessel steels and other alloys.However, the capability of PDs (vacancies and self-interstitials) to carry solute atoms to the nucleation sites, although often inferred in simple terms from the solute-PD binding energies, is yet not fully characterized. Nowadays, precise analytical models based on the Self-Consistent Mean Field (SCMF) theory [25] or the Green-function approach [26], in combination with ab initio calculations of defect jump rates, allow for a highly accurate analysis of the intrinsic atomic-transport properties by calculation of the transport (Onsager) matrix [27]. By the latter methods, it has been proven that solute drag by vacancies is a widespread phenomenon arising below a given temperature threshold in body-centered cubic (bcc) [28,29], face-centered cubic (fcc) [30,31,32], and hexagonal close-packed (hcp) metals [33], provided that the vacancy-solute interaction is sufficiently strong.In dilute ferritic alloys, the threshold temperature has been systematically determined for all transition-metal impurities [34,29]. This threshold is near or above 1000 K for Cu, Mn, Ni, P, and Si, whereas it lies near 300 K for Cr. Therefore, vacancies are indeed capable of transporting all solutes to sinks (including nucleation sites), with the exception of Cr for which depletion at sinks is expected.On the other hand, the transport efficiency of self-interstitial atoms (SIA) has been only superficially investigated. Speculations based on ab initio evaluations of the stability of mixed dumbbells (MD) [35,36,37], and the interpretation of resistivity-recovery (RR) experiments [38,...

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Section: Comparison With Experimental Ris Observationssupporting

confidence: 90%

mentioning

confidence: 99%

Solute diffusion by self-interstitial defects and radiation-induced segregation in ferritic Fe–X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

et al. 2020

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“…The combination of high stability and fast diffusion leads to very long MFP's, which in the case of P is consistent with the observed heavy segregation at grain boundaries or dislocations [26]. Concerning the other species, the V-Cu and V-Si complexes are more stable than V-Mn and V-Ni because of the larger binding energy (in first approximation E diss can be estimated as the sum of binding and migration energy [14]), Finally, the computed MFP of the V-Ni pair is shorter than the other solutes with similar drag tendencies (Mn, Cu).…”

Section: Vacancy-solute Pairs In Dilute Alloyssupporting

confidence: 83%

Stability and mobility of small vacancy–solute complexes in Fe–MnNi and dilute Fe–X alloys: A kinetic Monte Carlo study

Messina

Malerba

Olsson

2015

Nuclear Instruments and Methods in Physics Research Section B:

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a b s t r a c tManganese and nickel solute atoms in irradiated ferritic steels play a major role in the nanostructural evolution of reactor pressure vessels (RPV), as they are responsible for the formation of embrittling nanofeatures even in the absence of copper. The stability and mobility of small vacancy-solute clusters is here studied with an atomistic kinetic Monte Carlo approach based on ab initio calculations, in order to investigate the influence of Mn and Ni on the early life of small radiation-induced vacancy clusters, and to provide the necessary parameters for advanced object kinetic Monte Carlo simulations of the RPV longterm nanostructural evolution. Migration barriers are obtained by direct ab initio calculations or through a binding energy model based on ab initio data. Our results show a clear immobilizing and stabilizing effect on vacancy clusters as the solute content is increased, whereas the only evident difference between the two solute species is a somewhat longer elongation of the cluster mean free path in the presence of a few Mn atoms.

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“…1. To start with, APT frequently reveals segregation of solute atoms on various crystal defects such as dislocation lines, grain boundaries or carbide matrix interfaces in irradiated RPV steels [16][17][18][19][20][21][22][23]32]. This clearly supports the hypothesis that solute atoms are continuously dragged by single point defects towards point-defect sinks, irrespective of the magnitudes of solute-solute interactions.…”

Section: Experimental Evidencesupporting

confidence: 53%

The Dominating Mechanisms for the Formation of Solute-Rich Clusters in Steels under Irradiation

et al. 2019

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The formation of nano-sized, coherent, solute-rich clusters (NSRC) is known to be an important factor degrading the macroscopic properties of steels under irradiation. The mechanisms driving their formation are still debated. This work focuses on low-Cu reactor pressure vessel (RPV) steels, where solute species are generally not expected to precipitate. We rationalize the processes taking place at the nanometre scale under irradiation, relying on the latest theoretical and experimental evidence on atomic-level diffusion and transport processes. These are compiled in a new model, based on the object kinetic Monte Carlo (OKMC) technique. We evaluate the relevance of the underlying physical assumptions by applying the model to a large variety of irradiation experiments. Our model predictions are compared with new experimental data obtained with atom probe tomography and small angle neutron scattering, complemented with information from the literature. The results of this study reveal that the role of immobilized selfinterstitial atoms (SIA) loops dominates the nucleation process of NSRC.

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Atom probe tomography characterizations of high nickel, low copper surveillance RPV welds irradiated to high fluences

Cited by 97 publications

References 12 publications

Solute diffusion by self-interstitial defects and radiation-induced segregation in ferritic Fe–X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

Solute diffusion by self-interstitial defects and radiation-induced segregation in ferritic Fe–X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

Stability and mobility of small vacancy–solute complexes in Fe–MnNi and dilute Fe–X alloys: A kinetic Monte Carlo study

The Dominating Mechanisms for the Formation of Solute-Rich Clusters in Steels under Irradiation

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