Modeling the dislocation-void interaction in a dislocation dynamics simulation
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Modeling the dislocation-void interaction in a dislocation dynamics simulation Sylvain Queyreau1,4, Ghiath Monnet2, Brian D. Wirth3 and Jaime Marian4 1
Nuclear Engineering Dept., UC Berkeley, Berkeley, CA 94720, USA. EDF-R&D, MMC Dept., Avenue des Renardieres, 77818 Moret-sur-Loing, France. 3 Nuclear Engineering Dept., University of Tennessee, Knoxville, TE 37996, USA. 4 Lawrence Livermore National Laboratory, P. O. Box 808, Livermore, CA 94551, USA. 2
ABSTRACT In this paper, we propose a model for dislocation-void interaction in Iron that is amenable to dislocation dynamics simulations. Voids are treated as shearable particles whose shear resistance and thermal activation parameters are obtained from atomistic calculations. The modeling is first validated by direct comparison with molecular dynamics calculations. A good agreement is found especially at 0K and high temperature. The interaction with a random distribution of voids is then investigated. INTRODUCTION Irradiation-induced defects produced in nuclear power plants are known to impact the mechanical properties of structural components, e.g. yield stress increases and loss of ductility. The nature and properties of irradiation defects depends upon the irradiated material. In the case of ferritic steels, such as those used for reactor pressure vessels, vacancy clusters, or voids, are of particular interest as highlighted by early atomistic simulations [1]. One of the remaining challenges in the prediction of the long-term behavior of irradiated materials is to account for mechanisms associated with different scales of length and time. Indeed, the detail of the dislocation-void interaction can only be described at the atomistic scale [1,2] whereas the plastic flow is controlled by collective behaviors of dislocations and their interaction with obstacles. Extensive work has been performed in the past decade at the atomistic scale to understand void strengthening [1-5]. It has been shown that: (i) voids are indeed strong obstacles to dislocations; (ii) the critical stress required to pass voids is significantly affected by temperature; (iii) even though analytical models [6] can estimate the strengthening effect of an individual void [2], considering the temperature dependence and experimental obstacle distributions remains difficult. At a larger scale, Dislocation Dynamics (DD) is ideally suited to investigate the irradiation strengthening. However, only few studies of this kind currently exist [7,8]. In this paper, we described a DD modeling for dislocation-void interactions in Iron. First, we explain the technical solutions adopted, then the modeling is validated at 0 K, followed by a comparison of the simulated temperature dependence of the void strengthening to recent atomistic results. Finally the strengthening due to a random distribution of voids is investigated. THEORY Most of the MD work [1,2,4] has been performed for edge dislocations since their mobility is much simpler than for screw character [9,10]. Consequently, the present investigation
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