Simulation de la cinétique d’absorption des défauts ponctuels par les dislocations et amas de défauts

Denise Carpentier 1
1 SRMP - Service de recherches de métallurgie physique
DMN - Département des Matériaux pour le Nucléaire : DEN/DMN
Abstract : Cluster Dynamics (CD) is a mean field simulation method which makes it possible to predict the materials evolution under irradiation. In this work, we focus on sink strengths, which are the parameters used in CD to represent the capacity of sinks (dislocations, cavities…) to absorb point defects (vacancies, self-interstitials). To calculate the sink strengths, object kinetic Monte Carlo (OKMC) simulations are performed. The energy of point defects at stable and saddle points is described through their elastic dipoles. These elements are computed in an aluminum crystal using density functional theory. In a first part, the sink strengths of the main objects found in irradiated microstructures (dislocations, cavities and dislocation loops) are calculated on simple configurations. This study reveals the importance of elastic interactions, and enables us to identify the saddle point anisotropy of point defects as an important parameter, as it modifies both the point defects trajectories and the sink strength values. Then, we focus on the role of the relative position of sinks in their capacity to absorb point defects. Microstructures containing a large number of dislocation loops are generated by OKMC simulations and the absorption of point defects by those microstructures is measured. It is shown that the neighborhood of a sink modifies noticeably its capacity to absorb the point defects and this behavior is rationalized through the Voronoi volume associated with each sink. This study leads to the proposal of a new sink strength expression, and of a new formalism for CD in which clusters are described by their size and their Voronoi volume. The results show that this formalism makes it possible to strongly improve the prediction of the evolution of cluster size distributions during irradiation.
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Denise Carpentier. Simulation de la cinétique d’absorption des défauts ponctuels par les dislocations et amas de défauts. Science des matériaux [cond-mat.mtrl-sci]. Université Paris-Saclay, 2018. Français. ⟨NNT : 2018SACLX077⟩. ⟨tel-01915303⟩

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