The diffusion behaviors of interstitial impurities in V-4Cr-4Ti alloys under ion irradiation

NIFS HEAT-1 and four types of the V-4Cr-4Ti alloys with different oxygen and nitrogen content were irradiated with Cu²⁺ ions at 973 K up to dose of 10 dpa. In this irradiation condition, the flux of oxygen, which through the surface is estimated about 2-4 × 10¹⁶ (s m²)^-1, and the oxygen levels in specimens are calculated by finite difference method. In the cases of high purity specimens, oxygen diffused from the surface into the irradiated region. Moreover, oxygen diffused from the back of the irradiated surface into the irradiated region and enhanced the precipitations at the irradiated region. It is shown that the initial impurity level and flux of oxygen, which diffused from the atmosphere, essentially limited the precipitation behavior.