Impact of defect annihilation mechanism on the grain size dependence and the dimensionality effect of radiation induced segregation

Abstract

Radiation-induced segregation (RIS) of alloying elements at defect sinks critically affects material performance. This work computes and compares RIS at grain boundaries in a Fe-Ni-Cr alloy for a wide range of grain sizes with 1D, 2D, and 3D models. A transition in grain size dependence from linear to gradual convergence is identified, along with a dimensionality effect in modeling RIS using 1D and 2D models compared with more realistic 3D models. Further analysis shows that both the grain size dependence and the dimensionality effect are governed by the defect annihilation mechanism. In the absorption dominated regime, 1D and 2D models overestimate RIS, and RIS depends linearly on grain size. In the recombination dominated regime, the dimensionality effect vanishes gradually, and RIS converges gradually over grain size. The dimensionality effect can be corrected using the ratio of recombination over sink absorption, allowing for realistic RIS simulation using the 1D model.