THE EFFECTS OF OVERSIZED SOLUTE ADDITION ON MICROSTRUCTURAL EVOLUTIONIN FE-CR-NI ALLOYS DURING ELECTRON-IRRADIATION

Defect cluster formation under electron irradiation in an Fe-Cr-Ni aus tenitic pure ternary alloy and alloys containing over-sized solutes (n iobium and titanium) has been investigated with a HVEM at temperatures between 293 K and 873 K. The interstitial loop density and its temper ature dependence, which were drastically changed by small addition of sub-sized solute (P, Si and S), were not affected by titanium and niob ium additions. Above 423 K, vacancy type defects clusters (loop and SF T) were formed in the pure ternary alloy along with interstitial loops . By niobium (titanium) additions, on the other hand, formation of a v acancy defect cluster below 450 K was Strongly suppressed. These pheno mena seemed to be due to the low and high binding energies of intersti tial-solute and vacancy-solute, respectively.