Micro-scale signature for suppressing fragile fracture in high entropy alloys under irradiation

Compared with traditional alloys, high entropy alloys (HEAs) have better resistance to irradiation embrittlement and hardening, which continue to gain significant attention as promising high-end structural materials, but up until now, the underpinnings of suppressing brittle failure are yet to be revealed, limiting their application. Hence, this study proposes a molecular dynamics framework that can apprehend the evolutions of nano-scale dislocations and micron-sized shear bands from a microstructural evolution-energetics standpoint to elucidate deformation mechanisms in FeNiCrCuAl HEAs under irradiation. Accordingly, prototypic models (0 dpa, 0.02 dpa and 0.2 dpa) of the HEA, indicated an ultimate tensile strength at equivalent strain point of 4.7 % but as strengths declined with the progression of strain, multiple irradiations provoked intense atomic-dislocation interactions by which higher dislocation densities stimulated high-energy dislocation intersects for an amplified work-hardening effect. The evolutions of dislocation density with variations in average atomic energies precipitated distinctive shear band mechanisms characterized by multiple shear bands propagations along 45° and 135° directions in all of the models, and by the atomic level internal stresses constraint on atomic mobility under negative pressure, lowered atomic energies induced by intensified irradiations evolved a phenomenal cross-blocking effect of fewer multiple propagating shear bands to indicate higher ultimate tensile strength and enhanced resistance to fragile failure in the HEAs. Thus, by capturing the dislocation-shear band mechanism under irradiated energy potential landscape, the correlation between micro-scale structural evolutions and mechanical behavior was established in unraveling the fragile failure phenomenon in HEAs.