A Cluster Dynamics Study on Dislocation Loops in Fecral Alloy

Abstract

FeCrAl alloy has fine swelling resistance due to the additional a<100> dislocation loops (in addition to the conventional a/2<111> loops in bcc alloy) generated under irradiation. However, most previous simulation studies about irradiated FeCrAl alloy treat these two types of dislocation loops as one kind of loop. In fact, the characteristics and evolutions of these two types of dislocation loops are very different, which will produce different irradiation effects at macro scale. This work innovatively establishes the cluster dynamics rate theory model considering two types of dislocation loops simultaneously in FeCrAl alloy. The model considers the concentrations of two types of loops in rate equations, direct formation of clusters in cascade, as well as the migration of clusters with two types of Burgers vector and the resulting flow in cluster phase space. Therefore, this simulation is close to the real physical process and observation results. With this cluster dynamics model, the number densities, average sizes and size distributions of two types of dislocation loops in Fe13+ ion irradiated FeCrAl alloy are calculated. The simulation results fit well with the experimental results as a whole, which verifies the correctness of cluster dynamics model used in this work. On this basis, the long-term evolutions of two types of dislocation loops and voids in high-dose neutron irradiated FeCrAl alloy under different temperatures are simulated. Simulation results show that the fraction of a<100> loops increases with the dose first, then becomes saturated and almost unchanged, which is equal to the fraction of a<100> loops formed in cascade. Although this cluster dynamics model is relatively preliminary and simple, it still has certain significance for exploring the two types of dislocation loops in irradiated FeCrAl alloys and this model will continue to be developed and deepened.

Keywords: Two types of dislocation loops, cluster dynamics, irradiation, FeCrAl alloy