On α′ precipitate composition in thermally annealed and neutron-irradiated Fe- 9-18Cr alloys

Reese, Elaina R.; Bachhav, Mukesh; Wells, Peter; Yamamoto, Takuya; Odette, G.R.; Marquis, Emmanuelle A.

doi:10.1016/j.jnucmat.2017.12.036

Cited by 61 publications

(25 citation statements)

References 41 publications

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“…It must be emphasized that it is not the case in this work and in previous works where plateaus were observed [7,29]. It is worth noting that increase in Cr concentration with size is difficult to interpret [13] as it is difficult to separate artefact from kinetics effects. Indeed, interphase surface energy is one of the main factor determining the Cr content of the clusters in Fe-Cr [46] and the composition of the clusters can differ from equilibrium composition of the α′ phase [47,48].…”

Section: Atom Probe Tomography Characterizationcontrasting

confidence: 52%

“…Thus, a thorough understanding of the mechanisms involved during thermal ageing or irradiation of FeCr alloys is a key issue. In particular, the characterization of the α′ precipitation, well known for embrittling alloys, has been carried out after thermal ageing [6,7] and after several irradiation conditions [8][9][10][11][12][13]. Small Angle Neutron Scattering (SANS) as well as Atom Probe Tomography (APT) are frequently used to study α -α′ decomposition as they are well suited for characterizing nanoscale precipitates.…”

Section: Introductionmentioning

confidence: 99%

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Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy

Tissot

Pareige

Mathon

et al. 2019

Materials Characterization

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A B S T R A C Tα′ precipitation in a Fe-19 at.%Cr alloy aged at 500°C up to 2008 h has been characterized by both APT and SANS. This paper shows that when using an appropriate method for SANS data treatment, both APT and SANS yield consistent results regarding not only volume fraction and size but also α and α′ composition. Good agreement is achieved when α′ particles are considered as magnetic scattering features at the early stage of the kinetics.

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Section: Atom Probe Tomography Characterizationcontrasting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy

Tissot

Pareige

Mathon

et al. 2019

Materials Characterization

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“…Other data in literature shows a wide variety of Cr compositions ranging from 40-80 [15] and 55-60% [8,12] for neutron irradiations, which is much less than predicted by the phase-field simulations. However, the APT compositions are strongly dependent of the precipitate size, especially below 1.5 nm [15,81]. The Fe content α' in precipitates less than 1-2 nm in radius is overestimated in APT, primarily due to so-called trajectory aberrations, that result in an interface mixing zone containing both matrix and precipitate atoms [82,83].…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

Flux effects in precipitation under irradiation – Simulation of Fe-Cr alloys

Reese

Marquis

et al. 2019

Acta Materialia

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Radiation-enhanced precipitation of Cr-rich α' in irradiated Fe-Cr alloys, which results in hardening and embrittlement, depends on the irradiating particle and the displacement per atom (dpa) rate. Here, we utilize a Cahn-Hilliard phase-field based approach, that includes simple models for nucleation, irradiating particle and rate dependent radiation-enhanced diffusion and cascade mixing to simulate α' evolution under neutrons, heavy ions, and electron irradiations. Different irradiating particles manifest very different cascade mixing efficiencies. The model was calibrated using neutron data. For cascade inducing neutron/heavy-ion dpa rates at 300 °C between 10 -8 and 10 -6 dpa/s the model predicts approximately constant number density, decreasing radius, decreasing α' Cr composition, and lower α' volume fraction. The model then predicts a dramatic transition to no α'formation above approximately 10 -5 dpa/s, while electron irradiation, with weak mixing, had little effect at dpa rates up to 10 -3 dpa/s. These model predictions are consistent with experiments. We explain the results in terms of the flux dependence of the radiation enhanced diffusion, cascade mixing, and their ratio, which all vary significantly in relevant flux ranges for neutron and cascade inducing ion irradiations. These results show that both cascade mixing and radiation enhanced diffusion must be accounted for when attempting to emulate neutron-irradiation effects using accelerated ion irradiations. flux effects by triple-beam ions at 450 °C to 10 dpa [17]. Pareige et al. recently reported an APT study of Fe-12Cr under heavy-ion irradiation at 1×10 -4 dpa/s at 300 °C that observed a low density of dilute Cr clusters after irradiation to 0.5 dpa [18]. Likewise, Marquis et al. [19] found no α' in Fe-15Cr irradiated by Fe ++ ions at a dose rate of 1×10 -4 dpa/s up to 60 dpa at 300 °C, but observed a small density clusters with only 35-50 at.% Cr in in a Fe-15Cr at a lower dose rate of ≈ 1×10 -5 dpa/s, suggesting a pronounced dose rate effect [19]. Korchuganova et al. carried out a heavy-ion irradiation at room temperature on a Fe-22Cr alloy that was pre-aged at 500 °C to form α' precipitates with a distribution of sizes [20]. APT showed that the heavy-ion irradiation dissolved the small preexisting α' precipitates and made the larger ones more diffuse. A similar effect of heavy-ion irradiation was also shown to retard spinodal decomposition of Cr-rich α' in a duplex stainless steel with 20 wt.% Cr at 300 °C [21]. In contrast to the heavy-ion irradiation microstructures, Tissot et al. reported that a 3.9×10 -5 dpa/s electron irradiation at 300 °C accelerated precipitation of near equilibrium α' [22]. Accelerated α' precipitation under neutron irradiation has been attributed to radiation-enhanced diffusion (RED). RED depends on both temperature and dose rate due to the corresponding effect on vacancy and self-interstitial atom recombination mediated concentrations through a variety of mechanisms. However, a dose rate effect on RED does not full...

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“…At medium driving force, when non-classical nucleation is expected, the composition of the clusters differs from equilibrium composition of the a 0 phase [20,23]. The study of a 0 precipitation kinetics performed under thermal ageing and under irradiation using APT [7,12,24] has shown that at longer ageing time or higher irradiation dose, when the particle radius exceeds 2 nm, the equilibrium composition is reached. At early stage, when radius ranges between 1 and 2 nm, Cr content of the particles increases from 50 to 60 at.% to the equilibrium composition.…”

Section: Introductionmentioning

confidence: 99%

“…One way to deal with this problem is to plot the Cr concentration in a 0 particles with respect to their radius [7,12,24]. Nevertheless, this method poses a problem when mixing up data originating from different ageing conditions (temperature, thermal ageing and irradiation) and different alloys (different composition i.e.…”

Section: Introductionmentioning

confidence: 99%

Quantification of APT physical limitations on chemical composition of precipitates in Fe–Cr alloys

Hatzoglou

Radiguet

Costa

et al. 2019

Journal of Nuclear Materials

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a b s t r a c tAmong the different nano-features at the origin of embrittlement of FeeCr alloys and steels, a 0 precipitates play a major role in alloys with Cr content higher than about 10at.%. If Atom Probe Tomography (APT) is recognized as an efficient technique for characterizing a 0 precipitates, discussions remain on its ability to measure the actual composition of small particles. Two APT limitations are at the origin of these discussions: its lateral resolution (and on a smaller scale the depth resolution) and local magnification effects due to the difference in field evaporations between the matrix and the particles. In this study, the impacts of these two limitations are quantified for the first time using numerical approaches and an analytical model. This will provide an overview of the interpretation for the a' particles chemical composition experimentally measured by APT.The results show that: (i) the major effect of local magnification is ion focussing with no mixing in the core of the particles for particle radius larger than 1 nm, (ii) lateral resolution is the main contributor to the composition bias. Depending on the lateral resolution, the core of the small particles may be diluted by matrix atoms but the dilution does not exceed 5.2 at.%. The extent of the decrease in measured Cr concentration of the particles depends on the Cr concentration difference between particles and the surrounding matrix.

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On α′ precipitate composition in thermally annealed and neutron-irradiated Fe- 9-18Cr alloys

Cited by 61 publications

References 41 publications

Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy

Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy

Flux effects in precipitation under irradiation – Simulation of Fe-Cr alloys

Quantification of APT physical limitations on chemical composition of precipitates in Fe–Cr alloys

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On α′ precipitate composition in thermally annealed and neutron-irradiated Fe- 9-18Cr alloys

Cited by 61 publications

References 41 publications

Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy

Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy

Flux effects in precipitation under irradiation – Simulation of Fe-Cr alloys

Quantification of APT physical limitations on chemical composition of precipitates in Fe–Cr alloys

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Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy

Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy