A neutron-spectroscopy study of the local vibrations, the interstitial sites and the solubility limit of hydrogen in niobium-molybdenum alloys

We studied by neutron spectroscopy, and for temperatures from 10 to 300 K, the local vibrations of hydrogen interstitials in two niobium-based alloys containing 5 and 20 at.% molybdenum (Nb0.95Mo0.05H0.03 and Nb0.8Mo0.2H0.05) . Within experimental accuracy, the vibrational energies agree with those o f hydrogen in pure niobium. This indicates that the hydrogen in the two all oys occupies tetrahedral interstitial sites. At 10 K, the values of the vib rational energies show a complete hydrogen precipitation in the Nb0.95Mo0.0 5H0.03 alloy and no hydrogen precipitation in the Nb0.8Mo0.2H0.05 alloy. Th e fact that the hydrogen in the latter alloy was still in solid solution me ans that the molybdenum alloy components lead to an increase of the solubil ity limit of the hydrogen. (C) 2001 Elsevier Science BN. All rights reserve d.