Precipitation kinetics of Al3Zr and Al3Sc in aluminum alloys modeled with cluster dynamics

Precipitation kinetics of Al3Zr and Al3Sc in aluminum supersaturated solid solutions is studied using cluster dynamics, a mesoscopic modeling technique which describes the various stages of homogeneous precipitation by a single set of rate equations. The only parameters needed are the interface free energy and the diffusion coefficient which are deduced from an atomic model previously developed to study the same alloys. A comparison with kinetic Monte Carlo simulations based on the vacancy diffusion mechanism shows that cluster dynamics correctly predicts the precipitation kinetics provided a size dependent interface free energy is used. It also manages to reproduce reasonably well existing experimental data.Comment: Acta Mater. (2005), in pres

Cluster Dynamics Modeling of Materials: Advantages and Limitations

The aim of this paper is to give a short review on cluster dynamics modeling in the field of atoms and point defects clustering in materials. It is shown that this method, due to its low computer cost, can handle long term evolution that cannot, in many cases, be obtained by Lattice Kinetic Monte Carlo methods. Indeed, such a possibility is achieved thanks to an important drawback that is the loss of space correlations of the elements of the microstructures. Some examples, in the field of precipitation and irradiation of metallic materials are given. The limitations and difficulties of this method are also discussed. Unsurprisingly, it is shown that it goes in a very satisfactory way when the objects are distributed homogeneously. Conversely, the source term describing the primary damage under irradiation, by nature heterogeneous in space and time, is tricky to introduce especially when displacement cascades are produced

Precipitation in Al-Zr-Sc alloys: a comparison between kinetic Monte Carlo, cluster dynamics and classical nucleation theory

Zr and Sc precipitate in aluminum alloys to form the Al\_3Zr\_xSc\_{1-x} compound which, for low supersaturations of the solid solution, exhibits the L1\_2 structure. The aim of the present study is to model at an atomic scale the kinetics of precipitation and to build mesoscopic models so as to extend the range of supersaturations and annealing times that can be simulated up to values of practical interest. In this purpose, we use some ab initio calculations and experimental data to fit an Ising type model describing thermodynamics of the Al-Zr-Sc system. Kinetics of precipitation are studied with a kinetic Monte Carlo algorithm based on an atom-vacancy exchange mechanism. Cluster dynamics is then used to model at a mesoscopic scale all the different stages of homogeneous precipitation in the two binary Al-Zr and Al-Sc alloys. This technique correctly manages to reproduce both the kinetics of precipitation simulated with kinetic Monte Carlo as well as experimental observations. Focusing on the nucleation stage, it is shown that classical theory well applies as long as the short range order tendency of the system is considered. This allows us to propose an extension of classical nucleation theory for the ternary Al-Zr-Sc alloy.Comment: submitted for publication in "Solid-Solid Phase Transformations in Inorganic Materials", edited by TMS, 200

Corrosion sous contrainte assistée par l'irradiation en milieu primaire d'aciers inoxydables austénitiques

National audienceLes internes de cuves des REP sont soumis à divers modes de sollicitation, notamment de corrosion sous contrainte assistée par l'irradiation (IASCC). L'objectif de ce travail est d'étudier le couplage de plusieurs phénomènes physiques et chimiques interagissant en IASCC. En particulier, nous nous intéresserons au couplage microstructure (hétérogénéités chimique, cristallographique, nature des joints de grains...) / mécanismes de déformation / mécanismes d'irradiation / effet de l'environnement / champs mécaniques. Nous présenterons notamment la méthodologie et les premiers résultats concernant l'irradiation aux protons sur matériau massif et les essais de corrosion sous contrainte associés ; ainsi que la méthodologie concernant l'irradiation de lames minces qui sera effectuée sur la plate-forme JANNUS du CSNSM, où le matériau sera exposé simultanément à un faisceau d'irradiation et un faisceau d'implantation d'hélium

Using Cluster Dynamics to Model Electrical Resistivity Measurements in Precipitating Al-Sc Alloys

Electrical resistivity evolution during precipitation in Al-Sc alloys is modeled using cluster dynamics. This mesoscopic modeling has already been shown to correctly predict the time evolution of the precipitate size distribution. In this work, we show that it leads too to resistivity predictions in quantitative agreement with experimental data. We only assume that all clusters contribute to the resistivity and that each cluster contribution is proportional to its area. One interesting result is that the resistivity excess observed during coarsening mainly arises from large clusters and not really from the solid solution. As a consequence, one cannot assume that resistivity asymptotic behavior obeys a simple power law as predicted by LSW theory for the solid solution supersaturation. This forbids any derivation of the precipitate interface free energy or of the solute diffusion coefficient from resistivity experimental data in a phase-separating system like Al-Sc supersaturated alloys

EFFET DE L'IRRADIATION SUR LA DEMIXTION DES ALLIAGES MODELES FE-CR AUTOUR DE 15% DE CHROME

PALAISEAU-Polytechnique (914772301) / SudocSudocFranceF

Mécanismes de fragilisation sous irradiation aux neutrons d'alliages modèles ferritiques et d'un acier de cuve : amas de défauts

ROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF