LAUSR

In high Cr ferritic alloys, the α’ phase has been observed in a number of model and commercial alloys and under a variety of irradiation conditions, e.g.[1], and has been associated with increased hardening. Recent studies focused on binary Fe-Cr model alloys as surrogates for more complex Cr-containing ferritic steels. Atom probe tomography (APT) studies reported the presence of near-equilibrium nanoscale α’ precipitates in alloys containing above 9 % Cr that had been neutron irradiated at ≈ 315 C [2] at intermediate dose rates to 1.8 dpa. Post irradiation annealing at of a Fe-18%Cr binary alloy at 500°C partially dissolves and coarsens the precipitates, while annealing at 600°C fully dissolves them. These results are consistent with recent assessments of the Fe-Cr phase diagram. In contrast, wellformed nanoscale α’ precipitates have generally not been found under ion irradiation, that produce more diffuse diffuse and dilute Cr clusters instead [3].