Phase Separation Process in FeCr Alloys Studied by Neutron Small Angle Scattering

Furusaka, M.; Ishikawa, Yoshikazu; Yamaguchi, S.; Fujino, Y.

doi:10.1143/jpsj.55.2253

Cited by 46 publications

(13 citation statements)

References 18 publications

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“…The value of K after 10 h ageing at 773 K also agrees well with the reported modulation wavelength measured by APT, 5 see Table I. The obtained exponents (a 0 ¼ 0.10-0.11, a 00 ¼ 0.67-0.86) are in the same range as the available literature data, [6][7][8]10,12,26 although a 0 is slightly smaller than usually observed. This may be related to the early stages of decomposition studied, since the data presented in, e.g., Ref.…”

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confidence: 89%

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Early stages of spinodal decomposition in Fe–Cr resolved by in-situ small-angle neutron scattering

Hörnqvist

Thuvander

Steuwer

et al. 2015

Applied Physics Letters

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In-situ, time-resolved small-angle neutron scattering (SANS) investigations of the early stages of the spinodal decomposition process in Fe-35Cr were performed at 773 and 798 K. The kinetics of the decomposition, both in terms of characteristic distance and peak intensity, followed a power-law behaviour from the start of the heat treatment (a 0 ¼ 0.10-0.11 and a 00 ¼ 0.67-0.86). Furthermore, the method allows tracking of the high-Q slope, which is a sensitive measure of the early stages of decomposition. Ex-situ SANS and atom probe tomography were used to verify the results from the in-situ investigations. Finally, the in-situ measurement of the evolution of the characteristic distance at 773 K was compared with the predictions from the Cahn-Hilliard-Cook model, which showed good agreement with the experimental data (a 0 ¼ 0.12-0.20 depending on the assumed mobility). Spinodal decomposition of the bcc phase in Fe-Cr alloys into an Fe-rich and a Cr-rich phase is a widely studied phenomenon. The reason is two-fold: First, the system is the basis of the industrially important stainless steel family, where the decomposition of the bcc phase in ferritic, duplex and to some extent martensitic and d-ferrite containing austenitic grades, is partially responsible for degradation of the mechanical properties over time during elevated temperature exposure in service. Second, the Fe-Cr system is ideal to study the fundamentals of the spinodal decomposition process, since it offers a combination of a wide miscibility gap, a rather wide temperature range where the kinetics of the decomposition is suitable for practical measurements and minor coherency strains.The decomposition process in Fe-Cr is typically investigated by transmission electron microscopy (TEM), 1 M€ ossbauer spectroscopy, 2,3 atom probe tomography (APT), 4,5 or smallangle neutron scattering (SANS). [6][7][8] While each technique has its specific advantages, only SANS readily offers the possibility to perform time-resolved in-situ measurements at elevated temperatures. However, so far only very few investigations have taken advantage of this possibility of direct continuous tracking of the kinetics without any specimen-to-specimen variations in composition, starting structure, or isothermal temperature. For the Fe-Cr(-Ni) system, there are only two readily available reports of in-situ SANS experiments, 9,10 although other systems have been investigated more recently, e.g., Fe-Co-Mo. 11 In Refs. 9 and 10, acquisition times of several hours were used, which resulted in poor temporal resolution. Furusaka et al. 12 used in-situ SANS to investigate the critical scattering of Fe-Cr alloys in the vicinity of the Curie temperature, but the subsequent investigations of aged alloys were performed ex-situ.The existence and location of the spinodal in the binary Fe-Cr system are today rather well described, both from thermodynamic modelling and experiments (see, e.g., Ref. 13, and references therein). Direct observations from three dimensional APT investigations have also...

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confidence: 89%

“…9 and 10, acquisition times of several hours were used, which resulted in poor temporal resolution. Furusaka et al 12 used in-situ SANS to investigate the critical scattering of Fe-Cr alloys in the vicinity of the Curie temperature, but the subsequent investigations of aged alloys were performed ex-situ.…”

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confidence: 99%

Early stages of spinodal decomposition in Fe–Cr resolved by in-situ small-angle neutron scattering

Hörnqvist

Thuvander

Steuwer

et al. 2015

Applied Physics Letters

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“…This latter value is not inconsistent with the available experimental data on 3-D decomposition. 4,5 The kinetic parameters D 0 = 8 9 10 À23 m 2 /s and q = 0.9 entering the mobility formula (Eq. 8) were fitted against the diffusion data of Braun and FellerKniepmeier 18 and of Jönsson.…”

Section: Parameterization Of the Model And Comparison With Experimentsmentioning

confidence: 99%

“…Different techniques have been implemented. Bley 4 and Furusaka et al 5 studied the kinetics of phase decomposition of iron-chromium alloys containing various amounts of Cr by SANS, i.e., in the reciprocal space. Kuwano 6-8 performed Mössbauer spectroscopy measurements to study the kinetics of phase decomposition and tried to differentiate nucleation and growth regime from spinodal decomposition.…”

Section: Introductionmentioning

confidence: 99%

Spinodal Decomposition in Multilayered Fe-Cr System: Kinetic Stasis and Wave Instability

Maugis

Colignon

Mangelinck

et al. 2015

JOM

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Used as fuel cladding in the Gen IV fission reactors, ODS steels would be held at temperatures in the range of 350°C to 600°C for several months. Under these conditions, spinodal decomposition is likely to occur in the matrix, resulting in an increase of material brittleness. In this study, thin films consisting of a modulated composition in Fe and in Cr in a given direction have been elaborated. The time evolution of the composition profiles during aging at 500°C has been characterized by atom probe tomography, indicating an apparent kinetic stasis of the initial microstructure. A computer model has been developed on the basis of the Cahn-Hilliard theory of spinodal decomposition, associated with the mobility form proposed by Martin (1990). We make the assumption that the initial profile is very close to the amplitudedependent critical wavelength. Our calculations show that the thin film is unstable relative to wavelength modulations, resulting in the observed kinetic stasis.

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“…The kinetics of Cr clustering in Fe-Cr alloys has been studied extensively through experimental 26,[30][31][32][33][34] and theoretical approaches 27,34,35 . However, the effect of Cr precipitation on the magnetic properties of Fe-Cr alloys has largely been ignored from quantitative analysis.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of magnetism in Fe-Cr alloys with Cr clustering

Chapman

Dudarev

2019

Phys. Rev. B

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The dynamics of magnetic moments in iron-chromium alloys with different levels of Cr clustering show unusual features resulting from the fact that even in a perfect body-centred cubic structure, magnetic moments experience geometric magnetic frustration resembling that of a spin glass. Due to the long range exchange coupling and configuration randomness, magnetic moments of Cr solutes remain non-collinear at all temperatures. To characterise magnetic properties of Fe-Cr alloys, we explore the temperature dependence of magnetisation, susceptibility, Curie temperature and spinspin correlations with spatial resolution. The static and dynamic magnetic properties are correlated with the microstructure of Fe-Cr, where magnetisation and susceptibility are determined by the size of Cr precipitates at nominal Cr concentrations. The Curie temperature is always maximised when the solute concentration of Cr in the α phase is close to 5 to 6 at.%, and the susceptibility of Fe atoms is always enhanced at the boundary between a precipitate and solid solution. Interaction between Cr and Fe stimulates magnetic disorder, lowering the effective Curie temperature. Dynamic simulation of evolution of magnetic correlations shows that the spin-spin relaxation time in Fe-Cr alloys is in the 20 to 40 ps range. arXiv:1902.01645v1 [cond-mat.mtrl-sci]

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Phase Separation Process in FeCr Alloys Studied by Neutron Small Angle Scattering

Cited by 46 publications

References 18 publications

Early stages of spinodal decomposition in Fe–Cr resolved by in-situ small-angle neutron scattering

Early stages of spinodal decomposition in Fe–Cr resolved by in-situ small-angle neutron scattering

Spinodal Decomposition in Multilayered Fe-Cr System: Kinetic Stasis and Wave Instability

Dynamics of magnetism in Fe-Cr alloys with Cr clustering

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