Precipitation in proton- and ion-irradiated Alloy 625 Plus

Highlights: • Ion irradiation at dose rates above 10^-4 dpa/s at 300 °C causes disordering and dissolution of precipitates. • Non-equilibrium steady state nanoscale γ' and γ" microstructures develop under proton irradiations at 300 and 400 °C. • The Ni₃Si and Pt₂Mo-type ordered precipitates also formed under proton irradiations at 300 and 400 °C. • γ″ phase formation lowers the matrix Ni/Cr ratio and favors Pt₂Mo-type phase formation. Alloy 625 Plus is a commercial Ni-based alloy proposed as a candidate structural material for use in nuclear reactors. To clarify its microstructural evolution under relevant irradiation service conditions, we performed long term thermal aging, as well as proton and ion irradiations at ~300 and 400°C. While cascade mixing dominates during ion irradiation, diffusional processes allow the γ″, γ′, Ni₃Si, and Pt₂Mo-type ordered phases to form under proton irradiation. Moreover, comparison between solution treated and aged samples revealed steady state nanoscale patterning of the γ″ and γ′ phases and the dependence of the formation of the Pt₂Mo-type phase on the precipitation of γ″.