Microhardness tests were carried out on alloys after irradiation at 90 to 200C. It was found that the hardness increased with increasing irradiation temperature, except in the case of V-5Ti and V-5Nb. The hardening decreased upon increasing the irradiation temperature from 350 to 400C. Dislocation loops were observed after irradiation at temperatures ranging from 90 to 200C. No voids were observed at these irradiation temperatures. Positron annihilation spectroscopy revealed the nucleation of vacancy clusters in undersized binary alloys. The dislocation loop density increased with increasing irradiation temperature. It was concluded that irradiation hardening was caused mainly by dislocation loops. It was also suggested that interstitial O promoted dislocation loop nucleation since interstitial O and solute atoms interacted strongly at about 200C, leading to an enhanced nucleation of interstitial loops.

Microstructural Evolution and Hardening of Neutron Irradiated Vanadium Alloys at Low Temperatures. Y.Candra, K.Fukumoto, A.Kimura, H.Matsui: Journal of Nuclear Materials, 1999, 271-272, 301-5