Control of phosphorus inter-granular segregation in ferritic steels

Low- and high-alloy ferritic steels, 2.25Cr1Mo and E911, were irradiated by 250 keV Ni+ ions at 300 °C to study radiation-induced inter-granular phosphorus segregation behaviour and the effect of hafnium on radiation-induced segregation. Irradiations were carried out in an ion accelerator to a dose of 0.452 dpa for 2.25Cr1Mo and 0.305 dpa for E911 and E911+1%Hf. Grain boundary phosphorus segregation was detected by using field emission gun transmission electron microscopy with an energy dispersive X-ray analyzer. The phosphorus segregation at boundaries after irradiation in the high-alloy steel is higher than that in the low-alloy steel. Hafnium can suppress radiation-induced segregation to approximately one-sixth of the level in hafnium-free materials. A model to predict radiation-induced segregation in foil-samples is presented. Site competition between carbon and phosphorus is taken into consideration. The predicted results show good agreement with experimental data.