Irradiation hardening of pure vanadium and vanadium alloys due to helium ion implantation and displacement damage

Abstract Pure V and V–5Cr–5Ti were irradiated by He and high-energy heavy ions to various doses. Nanoindentation was used to characterize the hardness change induced by ion irradiation. Under high-energy heavy ions irradiation, the hardness of pure V increased rapidly and saturated at very low damage level (0.03 dpa), the hardness of V–5Cr–5Ti increased slowly and tended to saturate at the damage higher than 0.4 dpa. In contrast to high-energy heavy-ion irradiation, more significant hardening occurred in both pure V and V–5Cr–5Ti under He ion irradiation. The significant hardening induced by He ion irradiation at the low dose was probably from the coarsening of dislocation loops due to the existence of He atoms in materials. TEM results revealed that He bubbles with high density have been formed in V–5Cr–5Ti at the high dose. The estimation based on the dispersion barrier hardening model suggested that He bubbles exhibited as weak obstacles due to the limitation of size, the major contribution to hardening was considered to be from dislocation loops.