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Kinetic Paths of Radiation-Induced G-Phase Precipitation in Fe-MnNiSi Ferritic Model Alloys

48 Pages Posted: 4 Apr 2025 Publication Status: Under Review

See all articles by Quentin Tencé

Quentin Tencé

University of Paris-Saclay

Estelle Meslin

University of Paris-Saclay - DEN-Service de Recherches de Métallurgie Physique

Isabelle Mouton

University Grenoble Alpes - SIMaP

Brigitte Décamps

University of Paris-Saclay - Laboratoire de Physique des 2 infinis Irène Joliot-Curie (IJCLab)

Raphaëlle Guillou

University of Paris-Saclay - Service de Recherches Métallurgiques Appliquées

Jean-Luc Béchade

University of Paris-Saclay; Université Paris XI Sud - CEA

Erik Elkaim

Synchrotron SOLEIL

Anna Fraczkiewicz

MINES Saint-Étienne - Laboratoire Georges Friedel UMR 5307

Maylise Nastar

University of Paris-Saclay - Section of Physical Metallurgy

Abstract

A high-purity Fe-0.7Mn-1.8Ni-0.8Si model reactor pressure vessel alloywas irradiated with 22.5 MeV Fe9+ ions at 400◦C, producing a radiation dose of 1–2 dpa at a depth of 1μm, following by annealing at the same temperature for up to 34 weeks.  Irradiation led to the formation of fourMn-Ni-Si-enriched features: spherical precipitates in the bulk and on dislocation lines, sandwich-like precipitates, and toroidal segregation on dislocation loops. High-resolution transmission electron microscopy and synchrotron X-ray diffraction identified bulk precipitates as G-phase, exhibiting L21symme-try, a cube-on-cube orientation with the matrix, and semi-coherent interfaces. Atom probe tomography showed that the bulk G-phase precipitates have the formula Ni16(MnxFe1−x)6Si7, with increased Fe substitution in the Mn sub-lattice under irradiation. G-phase precipitates exhibited thermodynamic stability during post-irradiation annealing, while sandwich-like phases dissolved,indicating metastability. Heterogeneous precipitation of the G-phase on dis-location lines likely occurs through radiation-induced segregation (RIS) of Ni, Si, and Mn. Bulk sandwich-like precipitates with a dense Ni-Si-enriched phase in the center are certainly formed through a two-step mechanism: the SIAs clustering into a dense NiSi phase, followed by the kinetics of vacancy-solute clustering, leading to the precipitation of the less dense G-phase. The incubation time for homogeneous G-phase nucleation suggests a late blooming phase. While SIAs primarily influence phase selection, vacancies in excess lowers the solubility limit. Additionally, growing G-phase precipitates act as biased point defect sinks, promoting vacancy elimination, which may explain the absence of observed vacancy clusters in this alloy.

Keywords: Point defects Precipitation, Transmission electron microscopy (TEM), X-Ray Diffraction (XRD), Atom probe tomography (APT)

Suggested Citation

Tencé, Quentin and Meslin, Estelle and Mouton, Isabelle and Décamps, Brigitte and Guillou, Raphaëlle and Béchade, Jean-Luc and Elkaim, Erik and Fraczkiewicz, Anna and Nastar, Maylise, Kinetic Paths of Radiation-Induced G-Phase Precipitation in Fe-MnNiSi Ferritic Model Alloys. Available at SSRN: https://ssrn.com/abstract=5201584 or http://dx.doi.org/10.2139/ssrn.5201584

Quentin Tencé

University of Paris-Saclay ( email )

Estelle Meslin (Contact Author)

University of Paris-Saclay - DEN-Service de Recherches de Métallurgie Physique ( email )

Gif-sur-Yvette
France

Isabelle Mouton

University Grenoble Alpes - SIMaP ( email )

Grenoble
France

Brigitte Décamps

University of Paris-Saclay - Laboratoire de Physique des 2 infinis Irène Joliot-Curie (IJCLab) ( email )

Orsay, 91405
France

Raphaëlle Guillou

University of Paris-Saclay - Service de Recherches Métallurgiques Appliquées ( email )

Jean-Luc Béchade

University of Paris-Saclay ( email )

Université Paris XI Sud - CEA ( email )

15, rue Georges Clemenceau
Orsay cedex, 91405
France

Erik Elkaim

Synchrotron SOLEIL ( email )

L'Orme des Merisiers
91192 Gif-sur-Yvette
France

Anna Fraczkiewicz

MINES Saint-Étienne - Laboratoire Georges Friedel UMR 5307 ( email )

Saint-Etienne
France

Maylise Nastar

University of Paris-Saclay - Section of Physical Metallurgy ( email )

France

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