Swelling behavior of V–Fe binary and V–Fe–Ti ternary alloys

Abstract

V–Fe binary alloys with different Fe concentrations, i.e., V–1, 3 and 5 at.% Fe, and V–5% Fe alloy added with 1, 3 and 5 at.% of Ti were irradiated in EBR-II at 380–615°C to about 11 dpa. TEM observation was performed after irradiation. A systematic increase in cavity size was observed with increasing iron concentration in the binary alloys, especially at 510°C and 615°C irradiation. On the other hand, the density of cavities decreased with increasing iron concentration and irradiation temperature. Maximum swelling in V–Fe system occurred between 500°C and 600°C and the amount of swelling was up to 30% at a damage level of 11 dpa. The alloy containing only 1% Fe already showed substantial swelling. The effect of titanium addition to the swelling was very remarkable. One atomic percent of titanium addition to V–5 at.% Fe significantly suppressed cavity formation, and 3 at.% of titanium addition entirely suppressed swelling. There seems to be a threshold titanium concentration for suppression of swelling in V–5 at.% Fe. Radiation-induced precipitation of titanium oxide may be one reason why titanium additions suppress the swelling in vanadium alloys. Homogeneous titanium oxide precipitates were not observed so that the titanium in solution is more likely to be playing an important role for suppression of swelling.