Investigating sluggish diffusion in a concentrated solid solution alloy using ion irradiation with in situ TEM

Concentrated solid solution alloys (CSAs) – including high entropy alloys – are known for their remarkable mechanical and corrosion resistances with superior tolerance against the deleterious effect of irradiation exposure when compared with pure metals and dilute alloys. To date, however, the mechanisms responsible for such improvements are still unclear and remain a subject of investigation. The present work reports in situ Transmission Electron Microscopy (TEM) study under simultaneous ion irradiation of the face-centred cubic (FCC) FeCrMnNi quaternary CSA, comparing with a non-equiatomic Fe-based alloy, the AISI-348 austenitic stainless steel that has Cr, Ni and Mn as alloying elements. The alloys were irradiated under the same conditions, with 6 keV He+ and 134 keV Xe+ ions at 298 K up to 1.7 1017 ions⋅cm−2 (4 displacements-per-atom or dpa) and 2.7 1015 ions⋅cm−2 (4 dpa), respectively. The nucleation of inert gas bubbles was tracked upon post-irradiation extended annealing up to 673 K. He and Xe bubbles were observed to grow at a rate slightly slower in the CSA. Trends from the bubble size analyses show that the nucleation and growth of inert gas bubbles may be suppressed or delayed in some conditions in the CSA.