Void formation and precipitation in neutron irradiated vanadium alloys

Abstract

In order to investigate the effect of alloying elements on void formation and precipitation during neutron irradiation, V and V based alloys were irradiated in the experimental fast breeder reactor “JOYO” up to 1 × 1025 n/m2 at 670–870 K. Alloying elements were selected on the basis of volume size factors; C was selected as an interstitial atom, Cr as an example of an undersized substitutional atom, and Ti and Mo as examples of oversized ones. Voids were formed in almost all of the samples, with the exception of the V-C and V-Ti alloys. Precipitation was not observed in the V-Mo alloy, and homogeneous void formation occurred, where although the resultant swelling was not large. On the contrary, V-Cr alloy exhibited inhomogeneous void formation, and the swelling was larger than in V. Observations indicated that the void formation was related to the radiation-induced precipitates which nucleated on pre-existed dislocations. The void formation and precipitation behaviour are discussed terms of the effect of alloying.