Irradiation hardening behavior of high entropy alloys using random field theory informed discrete dislocation dynamics simulation

Abstract

High entropy alloys (HEAs) exhibit outstanding radiation resistance over traditional alloys owing to severe lattice distortion, and therefore, would be regarded as candidate materials for advanced reactors. However, the complex evolution of dislocation configurations in the irradiated HEAs subjected to the external loads has not been uncovered at the micron scale. To elucidate this key mechanism, we develop the random field theory informed discrete dislocation dynamics simulations based on high-resolution transmission electron microscopy, to systematically clarify the role of heterogeneous lattice strain on the complex interactions between the dislocation loop and dislocation in three-dimensional (3D) space. The results show that the lattice-strain-induced irradiation hardening decreases, in agreement with the excellent irradiation hardening resistance of the HEAs from the recent experiment. Based on the analysis of the micrometer-scale dislocation multiplication process, a new cross-slip mechanism through the collinear reaction between dislocations and rhombus perfect loops is revealed. The peaks and valleys of the heterogeneous lattice strains induced by severe lattice distortion are randomly distributed in a 3D space, reducing an aggregation of lattice point and dislocation density at the local region. The cross-slip process occurs by the joint action of the lattice distortion and rhombus-perfect-loop dislocation reaction, leading to the strong irradiation resistance attributed to a large number of narrow defect-free channel under a relatively random strain localization. The present study gives an insight into the fundamental irradiation damage behavior at the mesoscopic scale, thereby guiding the development of advanced HEA materials through the regulation of heterogeneous lattice strain for nuclear energy applications.