Irradiation-Induced Segregation at Dislocation Loops in CoCrFeMnNi High Entropy Alloy

To understand the redistribution of alloying element in high entropy alloys (HEAs) under irradiation, a CoCrFeMnNi alloy was irradiated with 1 MeV Kr ions at room temperature and 500oC, and characterized with atom probe tomography (APT) and transmission electron microscopy. At 500oC, Co and Ni were enriched at interstitial dislocation loops resulted from the ion irradiation. In contrast, no segregation was observed at interstitial dislocation loops formed at room temperature. It is inferred that the inverse Kirkendall effect through vacancy flux, as opposed to interstitial binding, was the primary mechanism attributing to the observed segregation. In addition, APT concentration contour plots show a ring-shaped segregation pattern instead of a disk-shaped pattern at the faulted dislocation loops, indicating the non-equilibrium nature of the defect clustering and solute segregation process of the CoCrFeMnNi under irradiation at high temperature.