Irradiation-Induced Solute Clustering in a Low Nickel FeMnNi Ferritic Alloy

Understanding the radiation embrittlement of reactor pressure vessel (RPV) steels is required to be able to operate safely a nuclear power plant or to extend its lifetime. The mechanical properties degradation is partly due to the clustering of solute under irradiation. To gain knowledge about the clustering process, a Fe-1.1 Mn-0.7 Ni (at.%) alloy was irradiated in a test reactor at two fluxes of 0.15 and 9 x10(17) n (E > 1MeV) .m (-aEuro parts per thousand 2).s (-aEuro parts per thousand 1) and at increasing doses from 0.18 to 1.3 x10(24) n (E > 1MeV) .m (-aEuro parts per thousand 2) at 300A degrees C. Atom probe tomography (APT) experiments revealed that the irradiation promotes the formation in the alpha iron matrix of Mn/Mn and/or Ni/Ni pair correlations at low dose and Mn-Ni enriched clusters at high dose. These clusters dissolve partially after a thermal treatment at 400A degrees C. Based on a comparison with thermodynamic calculations, we show that the solute clustering under irradiation can just result from an induced mechanism.