CORRELATION OF MICROSTRUCTURE AND TENSILE AND SWELLING BEHAVIOR OF NEUTRON-IRRADIATED VANADIUM ALLOYS

The microstructures of V-Ti, V-Cr-Ti, and V-Ti-Si alloys were characterized by transmission electron microscopy after neutron irradiation in the Fast Flux Test Facility (FFTF) at 420 and 600-degrees-C up to 114 dpa. Two types of irradiation-induced precipitates were identified, i.e., Ti2O and Ti5(Si,P)3. Thermal precipitates of Ti(O,N,C) were also observed in all unirradiated and irradiated specimens. Copious precipitation of the Ti5(Si,P)3 phase was associated with superior resistance to void swelling. In specimens with significant swelling, Ti5(Si,P)3 Precipitation was negligible. Ductility is significantly reduced when the precipitation of Ti20 and Ti5(Si,P)3 is pronounced. These observations indicate that initial composition, fabrication processes, and irradiation-induced precipitation are interrelated and are important factors to consider in developing an optimized alloy.