Radiation-induced bcc-fcc phase transformation in a Fe 3%Ni alloy

Belkacemi, Lisa T.; Meslin, E.; Décamps, B.; Radiguet, B.; Henry, J.

doi:10.1016/j.actamat.2018.08.031

Cited by 31 publications

(32 citation statements)

References 79 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For instance, Ni enrichment at dislocation loops has been observed to occur in FeNi alloys as Ni atoms bind with loops and then act as sinks for mobile defect-Ni complexes. This mechanism could be the precursor of the observed precipitation of the secondary phase [16]. Our results suggest that these complexes are likely to be vacancy-Ni pairs.…”

Section: Comparison With Experimental Ris Observationsmentioning

confidence: 57%

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

View full text Add to dashboard Cite

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,...

show abstract

Section: Comparison With Experimental Ris Observationsmentioning

confidence: 57%

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

View full text Add to dashboard Cite

show abstract

“…An intermetallic compound L1 0 -FeNi was found in meteorites * chuchun.fu@cea.fr but disputed to be stable [6] or metastable [7], with a critical ordering temperature, noted hereafter as T L1 0 -γ c , of 593 K determined from irradiated samples [8]. A yet more controversial issue is the existence of the metastable ordered phase of Fe 3 Ni, which was suggested to have a L1 2 structure but could not be fully confirmed by experiments [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Ground-state properties and lattice-vibration effects of disordered Fe-Ni systems for phase stability predictions

2020

Phys. Rev. Materials

View full text Add to dashboard Cite

By means of density functional theory, we perform a focused study of both body-centered-cubic (bcc) and face-centered-cubic (fcc) Fe-Ni random solid solutions, represented by special quasirandom structures. The whole concentration range and various magnetic configurations are considered. Excellent agreement on the concentration dependence of magnetization is found between our results and experimental data, except in the Invar region. Some locally antiferromagnetic fcc structures are proposed to approach experimental values of magnetization. Vibrational entropies of ordered and disordered systems are calculated for various concentrations, showing an overall good agreement with available experimental data. The vibrational entropy systematically contributes to stabilize disordered rather than ordered structures and is not negligible compared to the configurational entropy. Free energy of mixing is estimated by including the vibrational and ideal configurational entropies. From them, low-and intermediate-temperature Fe-Ni phase diagrams are constructed, showing a better agreement with experimental data than the one from a recent thermodynamic assessment for some phase boundaries below 700 K. The determined order-disorder transition temperatures for the L1 0 and L1 2 phases are in good agreement with the experimental values, suggesting an important contribution of vibrational entropy.

show abstract

“…Due to the complexity of RPV alloys, there will be many distinct species present and clusters will also have significant Fe content [20,86,87] and so when modelling triplet clusters, the configurational shape, chemistry and ordering of the triplet is also important. Finally, considering there is strong evidence that interstitial loops can act as nucleation points for the growth of solute clusters [39,43,88], it is likely that the energetic drive for clustering is a combination of interstitial loops, Cu precipitates and vacancy clusters.…”

Section: Fig 6 -Binding Enthalpies Of Triplet Clusters Containing Twmentioning

confidence: 99%

“…Atom probe tomography studies of these Mn-Ni-Si solute clusters have often found Cu cores surrounded by Ni, Mn, Si enriched shells [5,30,[36][37][38]. However, recent experiments have also found that clusters can develop in the absence of Cu [3,31,39,40] and solute-vacancy [41,42] and solute-interstitial [43,44] complexes develop in addition to pure solute clusters in both RPV steel and model alloys.…”

Section: Introductionmentioning

confidence: 99%

Understanding the importance of the energetics of Mn, Ni, Cu, Si and vacancy triplet clusters in bcc Fe

Whiting

Burr

King

et al. 2019

Journal of Applied Physics

View full text Add to dashboard Cite

Numerous experimental studies have found the presence of (Cu)-Ni-Mn-Si clusters in neutron irradiated reactor pressure vessel steels, prompting concerns that these clusters could lead to larger than expected increases in hardening, especially at high fluences late in life. The mechanics governing clustering for the Fe-Mn-Ni-Si system are not well-known; state-of-the-art methods use kinetic Monte Carlo (KMC) parameterised by density functional theory (DFT) and thermodynamic data to model the time evolution of clusters. However, DFT based KMC studies have so far been limited to only pairwise interactions due to lack of DFT data. Here we explicitly calculate the binding energy of triplet clusters of Mn, Ni, Cu, Si and vacancies in bcc Fe using DFT to show that the presence of vacancies, Si, or Cu stabilises cluster formation, as clusters containing exclusively Mn and/or Ni are not energetically stable in the absence of interstitials. We further identify which clusters may be reasonably approximated as a sum of pairwise interactions, and which instead require an explicit treatment of the three-body interaction, showing that the three-body term can account for as much as 0.3 eV, especially for clusters containing vacancies.

show abstract

Radiation-induced bcc-fcc phase transformation in a Fe 3%Ni alloy

Cited by 31 publications

References 79 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

Ground-state properties and lattice-vibration effects of disordered Fe-Ni systems for phase stability predictions

Understanding the importance of the energetics of Mn, Ni, Cu, Si and vacancy triplet clusters in bcc Fe

Contact Info

Product

Resources

About