Effects of Ni on evolution of interstitials and dislocation loops under uniaxial tensile stress in Fe-Ni system

Abstract

To understand the state of dislocation loops in iron (Fe)-based alloys under the application of external stress is important and necessary for elucidating their stress-induced preferential nucleation (SIPN), in which the regular arrangement of dislocation loops has been considered to play a key role. Different from previous studies, in this work, the coupled effects of Ni alloying and external stress on energy and kinetic evolution of the 1/2 < 111> loops in an Fe-Ni alloy were extensively studied through molecular dynamics (MD) simulations. The results indicate a suppression of such coupled effect on anisotropic distribution of loops formed after cascades. Further energy calculations imply that, compared to pure α-Fe, the normalized formation energy difference between dislocation loops with Burgers vector along the tensile and other directions is suppressed by Ni alloying. Similar trend is also observed in binding energy difference for an interstitial to bind with these loops. These results suggest that the preferential nucleation of loops can be suppressed by alloying atoms. Furthermore, from the viewpoint of energy barrier, more possible diffusion paths are explored under the coupled effect, revealing more possible rotations of 〈110〉 dumbbells and related 3D diffusion. The present work reveals that the effect of alloying elements in Fe-based alloy should be considered in employing the SIPN model to elucidate irradiation behavior of steels in nuclear reactors.