Physical insight into interactions of interstitial loops and dislocation lines in austenitic high entropy alloys: atomic-scale modelling

Nuclear reactor materials undergo significant changes in their microstructure and mechanical properties due to radiation exposure. Understanding the role of radiation-induced defects in these materials is a complex challenge, especially for new candidate material. This study utilizes molecular dynamics (MD) simulations with a novel interatomic potential to investigate the interactions between mobile edge dislocation lines and interstitial Frank loops within the quaternary model austenitic high entropy alloy (HEA) Cr15Fe46Mn17Ni22. This candidate alloy is referenced as "Y3-HEA". The behavior of this alloy is compared to that of a ternary alloy (Cr20Fe70Ni10) considered as a model of classical austenitic stainless steel (ASS). The investigation begins with molecular statics analysis, focusing on the unfaulting process of interstitial Frank loops. A simplified thermodynamic model is introduced to predict the critical size at which a Frank loop can undergo unfaulting. Complementing this, MD simulations explore several variables, including loop orientation, random seed configuration, temperature, loop size, and intersection interactions. Through this examination, interaction mechanisms between mobile edge dislocations and interstitial Frank loops in Y3-HEA are classified and comparisons are drawn with those observed in ASS. Furthermore, an average obstacle strength parameter is calculated for both ASS and Y3-HEA and its value is integrated into a radiation hardening constitutive model. This approach allows for the prediction of the contribution of dislocation loops to the hardening behavior of the studied alloys.