High Entropy Alloys (HEA) are metallic solid-solution alloys containing more than four elements in equivalent concentration, resulting in a high configurational entropy.

Our study focuses on increasing complexity FCC alloys, from pure metals to quaternary Fe-Mn-Ni-Cr. These high purity materials, designed at the EMSE (Ecole des Mines de Saint-Etienne) are ion irradiated at JANNUS facilities in CEA Saclay, under several ion types and radiation fluencies.

TEM, STEM and APT analysis reveals the impact of the irradiation dose and of the compositional complexity on the formation of defects: faulted and perfect dislocations loops, cavities and precipitates. More precisely, we investigate the type, size and density of loops, the precipitates structure, and the related chemical enrichment and depletion. In addition, we conducted experimental determinations of the stacking fault energy, which is a crucial parameter controlling the formation of defects.