Hydrogen traps in the oxide-alloy interface region of Zr-Nb alloys

In this study the H-1(N-15,alpha gamma)C-12 nuclear reaction has been used to measure hydrogen profiles of anodically oxidized Zr-Nb specimens containing various amounts of niobium. The profiles have been correlated with oxygen profiles, obtained using a Scanning Auger Microprobe (SAM), and with X-ray diffraction patterns. In addition, unoxidized Zr-2.5Nb (Zr-2.5 wt.% Nb) samples were implanted with oxygen and hydrogen to study the interaction between these two species when dissolved in the alloy. All the anodically oxidized specimens, except the pure Zr and the single-phase beta-Zr (Zr-20Nb) samples, displayed hydrogen peaks beneath the oxide layer. These results, in conjunction with the results from the implanted specimens, indicate that the hydrogen moves under the influence of a stress gradient to the sub-oxide region, where the metal lattice has been expanded due to superficial oxide growth. The results show that dissolved oxygen sites in Zr-2.5Nb alloy do not trap hydrogen.