Irradiation-induced grain boundary chromium microchemistry in high alloy ferritic steels

Lu, Zheng; Faulkner, R. G.; Was, G. S.; Wirth, Brian D.

doi:10.1016/j.scriptamat.2008.01.004

Cited by 104 publications

(60 citation statements)

References 13 publications

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“…The net result is an accumulation or a depletion of elements at these defect sinks, which can have deleterious effects on polycrystal properties. There have been a number of experimental studies to characterize and understand the mechanisms of radiation-induced segregation in a number of irradiated metal systems [3][4][5][6][7][8][9][10][11][12][13] as well as computational models. Interestingly, these models have to consider both the evolution of defect and defect clusters as well as their destinations.…”

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confidence: 99%

Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries inα-Fe

et al. 2012

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The energetics and length scales associated with the interaction between point defects (vacancies and self-interstitial atoms) and grain boundaries in BCC Fe was explored. Molecular statics simulations were used to generate a grain boundary structure database that contained ≈ 170 grain boundaries with varying tilt and twist character. Then, vacancy and self-interstitial atom formation energies were calculated at all potential grain boundary sites within 15Å of the boundary. The present results provide detailed information about the interaction energies of vacancies and selfinterstitial atoms with symmetric tilt grain boundaries in iron and the length scales involved with absorption of these point defects by grain boundaries. Both low and high angle grain boundaries were effective sinks for point defects, with a few low-Σ grain boundaries (e.g., the Σ3{112} twin boundary) that have properties different from the rest. The formation energies depend on both the local atomic structure and the distance from the boundary center. Additionally, the effect of grain boundary energy, disorientation angle, and Σ-designation on the boundary sink strength was explored; the strongest correlation occurred between the grain boundary energy and the mean point defect formation energies. Based on point defect binding energies, interstitials have ≈ 80% more grain boundary sites per area and ≈ 300% greater site strength than vacancies. Last, the absorption length scale of point defects by grain boundaries is over a full lattice unit larger for interstitials than for vacancies (mean of 6-7Å vs. 10-11Å for vacancies and interstitials, respectively).

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Section: Introductionmentioning

confidence: 99%

Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries inα-Fe

et al. 2012

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“…RIS in austenitic steels is well known and presents almost systematic trends: depletions of Cr and enrichments of Ni at grain boundaries. In ferritic steels, the experimental situation is far from being so clear: depletions and enrichments of Cr have been observed, without clear correlation with the irradiation conditions and the materials properties [3].Segregation and precipitation occur by formation, migration and elimination of point defects (vacancies and self-interstitials). We present a model that includes these mechanisms, and combines ab initio and atomistic kinetic Monte Carlo (AKMC) simulations.…”

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Atomistic Modelling of Segregation and Precipitation in Fe-Cr Alloys under Irradiation

Soisson

Jourdan

et al. 2016

EPJ Web of Conferences

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Iron-chromium alloys are the basis for ferritic and ferritic-martensitic steels that will be used in future fission (generation IV) and fusion nuclear reactors. With Cr content between typically 8 to 12% [1], or even 14% in the matrix of some oxide dispersion-strengthened steels [2], one can expect the precipitation of a Cr-rich α' phase that can be strongly accelerated under irradiation, due to point defect supersaturation. This precipitation can cause hardening and embrittlement. Radiation-induced segregation (RIS) is another important technological problem. It can lead to a Cr depletion at grain boundaries and therefore to a loss of corrosion resistance and again, to embrittlement. RIS in austenitic steels is well known and presents almost systematic trends: depletions of Cr and enrichments of Ni at grain boundaries. In ferritic steels, the experimental situation is far from being so clear: depletions and enrichments of Cr have been observed, without clear correlation with the irradiation conditions and the materials properties [3].Segregation and precipitation occur by formation, migration and elimination of point defects (vacancies and self-interstitials). We present a model that includes these mechanisms, and combines ab initio and atomistic kinetic Monte Carlo (AKMC) simulations. Migration barriers and jump frequencies are computed by using effective pair interactions with concentration and temperature dependences. Thanks to these dependences, the simulations are able to well reproduce the thermodynamic [4] and diffusion [5] properties of dilute and concentrated alloys, including the effects of the magnetic configurations and magnetic transitions, which are especially important in Fe-Cr alloys. They also give kinetics pf precipitation during isothermal annealing in good agreement with experimental studies [5].Simulations of α' precipitation under irradiation, predict that the kinetics can be considerably accelerated. For example, irradiations of alloys with 15 to 18%Cr at 290°C and a dose rate of 3.4×10 -7 dpa.s -1 produce a point defect supersaturations and therefore, an acceleration, of approximately 6-7 orders of magnitudes. To get a more precise estimation of the evolution of sink densities and point defect concentrations, cluster dynamics [6] have been used: the physical time scale of the Monte Carlo simulations is rescaled accordingly and one gets precipitation kinetics in good agreement with the few available experimental results [7,8]. The possible effect of ballistic mixing occurring in displacement cascades and the role of carbon, which is known to strongly interact with the vacancies, will be discussed.RIS results from the elimination of excess vacancies (V) and self-interstitials (I) on sinks such as dislocations, grain boundaries, or free surfaces. Permanent fluxes of point defects towards the sinks are then sustained, i.e. permanent fluxes of chemical species, leading to a modification of the local composition near the sinks. RIS can be analyzed properly in the framework of the thermodynamic...

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“…Як відомо, в матеріалах, які використовуються в ядерних реакторах, нейтронне опромінювання породжує нерівноважні точкові дефекти (вакансії та міжвузельні атоми) у великих концентраціях, а також лінійні та об'ємні структурні дефекти (дислокації, пори та виділення нової фази) [3,4].…”

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“…Експерименти показують [4][5][6][7][8][9][10][11][12][13], що під час опромінення сплаву при підвищених температурах (0.3 -0.5 T пл. ) [14] відбувається просторовий перерозподіл компонентів даного сплаву.…”

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Modeling Radiation-Induced Segregation in Binary Alloys

Skorokhod

Buhay

Bilyk

et al. 2018

EEJP

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A computer code to calculate the time and space dependencies of the defect and component concentrations of a binary alloy is developed. This code is based on the theoretical model for radiation-induced segregation governed by first and second Fick's laws with taking into account inverse Kirkendall effect. The system of three coupled partial differential equations for concentrations of one of components and point defects is converted to the system of ordinary differential equations in time by a discretization procedure. Numerical solutions of this system are obtained under appropriate initial and boundary conditions by means of the MATLAB. The modeling of radiation-induced segregation in binary Fe-Cr alloys is carried out for various initial concentrations of components, temperatures, dose rates and doses. радіаційно-індукованої сегрегації, що базується на першому та другому законах Фіка з урахуванням оберненого ефекту Кіркендала, розроблений комп'ютерний код, за допомогою якого для бінарних сполук знайдені просторова і часова залежності концентрацій компонентів та точкових дефектів. Система трьох зв'язаних диференціальних рівнянь в частинних похідних для концентрацій одного з компонентів та точкових дефектів процедурою дискретизації зводиться до системи звичайних диференціальних рівнянь за часом. Ця система чисельно розв'язується при заданих початкових та граничних умовах за допомогою пакету прикладних програм MATLAB. Проведено моделювання радіаційно-індукованої сегрегації в двокомпонентних сплавах Fe-Cr при різних початкових концентраціях компонентів, температурах, швидкостях утворення дефектів і набраних дозах опромінення. Продемонстрований процес досягнення стаціонарного стану при збільшенні дози опромінення. Розраховані профілі концентрації компонентів порівнюються з експериментально одержаними іншими авторами. Виконана оцінка чутливості моделі до вхідних параметрів та оцінюються її можливості. Даний комп'ютерний код розвинений для багатокомпонентних сплавів. КЛЮЧОВІ СЛОВА: матеріали реакторобудування, радіаційно-індукована сегрегація, двокомпонентні металеві сплави, профіль концентрації, точкові дефекти, обернений ефект Кіркендала, рівняння балансу, комп'ютерне моделювання В модели радиационно-индуцированной сегрегации, основанной на первом и втором законах Фика с учетом обратного эффекта Киркендалла, разработан компьютерный код, с помощью которого для бинарных соединений находится пространственная и временная зависимости концентраций компонентов и точечных дефектов. Система трех связанных дифференциальных уравнений в частных производных для концентраций одного из компонентов и точечных дефектов процедурой дискретизации приводится к системе обыкновенных дифференциальных уравнений по времени. Эта система численно решается при заданных начальных и граничных условиях с помощью пакета прикладных программ MATLAB. Проведено моделирование радиационно-индуцированной сегрегации в двухкомпонентных сплавах Fe-Cr при различных начальных концентрациях компонентов, температурах, скоростях образования дефектов и набранных...

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Irradiation-induced grain boundary chromium microchemistry in high alloy ferritic steels

Cited by 104 publications

References 13 publications

Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries inα-Fe

Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries inα-Fe

Atomistic Modelling of Segregation and Precipitation in Fe-Cr Alloys under Irradiation

Modeling Radiation-Induced Segregation in Binary Alloys

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