  The atomic-level tunability that results from alloying multiple transition
metals with d electrons in concentrated solid solution alloys (CSAs), including
high-entropy alloys (HEAs), has produced remarkable properties for advanced
energy applications, in particular, damage resistance in high-radiation
environments. The key to understanding CSAs radiation performance is
quantitatively characterizing their complex local physical and chemical
environments. In this study, the local structure of a FeCoNiCrPd HEA is
quantitatively analyzed with X-ray total scattering and extended X-ray
absorption fine structure methods. Compared to FeCoNiCr and FeCoNiCrMn,
FeCoNiCrPd with a quasi-random alloy structure has a strong local lattice
distortion, which effectively pins radiation-induced defects. Distinct from a
relaxation behavior in FeCoNiCr and FeCoNiCrMn, ion irradiation further
enhanced the local lattice distortion in FeCoNiCrPd due to a preference for
forming Pd-Pd atomic pairs.
