Atomistic Simulation of Vacancy and Self-Interstitial Diffusion in Fe-Cu Alloys
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ATOMISTIC SIMULATION OF VACANCY AND SELF-INTERSTITIAL DIFFUSION IN Fe-Cu ALLOYS Jaime Marian1, Brian D. Wirth1, J. Manuel Perlado2, G. R. Odette3 and T. Diaz de la Rubia1 1 Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, P. O. Box 808, L-353, Livermore, CA 94550, U.S.A. 2 Instituto de Fusión Nuclear, Universidad Politécnica de Madrid, C/ José Gutiérrez Abascal, 2; Madrid 28006, SPAIN 3 Department of Mechanical and Environmental Engineering, University of California, Santa Barbara, CA 93106, USA ABSTRACT Neutron hardening and embrittlement of pressure vessel steels is due to a high density of nanometer scale features, including Cu-rich precipitates which form as a result of radiation enhanced diffusion. High-energy displacement cascades generate large numbers of both isolated point defects and clusters of vacancies and interstitials. The subsequent clustering, diffusion and ultimate annihilation of primary damage is inherently coupled with solute transport and hence, the overall chemical and microstructural evolutions under irradiation. In this work, we present atomistic simulation results, based on many-body interatomic potentials, of the migration of vacancies, solute and self-interstitial atoms (SIA) in pure Fe and binary Fe-0.9 and 1.0 at.% Cu alloys. Cu diffusion occurs by a vacancy mechanism and the calculated Cu diffusivity is in good agreement with experimental data. Strain field interactions between the oversized substitutional Cu solute atoms and SIA and SIA clusters are predominantly repulsive and result in both a decreased activation energy and diffusion pre-factor for SIA and small (N
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