The stability of γ′ precipitates in a multi-component FeCoNiCrTi0.2 alloy under elevated-temperature irradiation

Abstract Precipitation hardening by γ′ precipitates is an effective strengthening mechanism for designing novel high-entropy alloys (HEAs). The stability of these γ′ precipitates under elevated temperature irradiation is a major concern for their application in nuclear industry. In the present study, a γ′-strengthened FeCoNiCrTi0.2 HEA is irradiated using 6.4 MeV Fe3+ ions at 400 °C, 500 °C and 600 °C, respectively. After irradiation, transmission electron microscopy (TEM) and atom probe tomography (APT) has characterized the structural and compositional stability of the γ′ precipitates. The results show that the ordered L12 structure of γ′ precipitate is susceptible to the radiation damage, whereas their basic compositional features can sustain up to ∼13 dpa at these temperatures. APT reveals that the dissolution of γ′ precipitates start from the surface of the precipitates at the early stage of irradiation. Dissolution and disordering of the precipitates are dependent on the irradiation dose and temperature. APT also shows that small Ni and Ti-rich clusters form after irradiation at elevated temperatures. The behavior of γ′ precipitates under irradiation is believed to be controlled by two competing factors, displacement damage and radiation enhanced diffusion. Both can influence the radiation induced disordering/dissolution and reprecipitation.