Cluster Dynamics Study of Defect Evolution in Neutron-Irradiated Dilute and Concentrated Fe-Cr Alloys


Cluster Dynamics Study of Defect Evolution in Neutron-Irradiated Dilute and Concentrated Fe-Cr Alloys

Gokhman, A. R.; Bergner, F.; Birkenheuer, U.; Ulbricht, A.

Cluster dynamics (CD) is used to study the evolution of the size distributions of vacancy clusters (VC), self-interstitial atom (SIA) clusters (SIAC) and Cr precipitates in neutron irradiated Fe-9at%Cr and Fe-12.5at%Cr alloys at T = 573 K with irradiation doses up to 1.5 dpa and a flux of 140 ndpa/s. Transmission electron microscopy (TEM) and small angle neutron scattering (SANS) data on the defect structure of this material irradiated at doses of 0.6 and 1.5 dpa are used to calibrate the model. For both alloys a saturation behavior was found by CD for the free vacancy and free SIA concentrations as well as for the number density of the SIAC above 0.006 dpa. The CD simulations also indicate the presence of VC with radii less than 0.5 nm and a strong SIAC peak with a mean diameter of about 0.5 nm, both invisible in SANS and TEM experiments. CD modeling of Cr precipitates has been done with taking into account of deviation of this system from the ideal cluster gas. A specific surface tension of about 0.17 J/m2 between the alpha matrix and the Cr-rich alpha' precipitate and the rate at which Cr monomers are absorbed about 7.94 m-1 were found as best fit values for reproducing the long-term Cr evolution in the irradiated Fe-12.5%Cr alloys observed by SANS.

Keywords: Cluster dynamics; neutron irradiation; chromium iron alloys; defects

  • Lecture (Conference)
    25th Research Workshop Nucleation Theory and Applications, 16.-23.04.2011, Dubna, Russia

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Publ.-Id: 15804