The mechanical properties of metals with body-centred cubic structure, such as niobium and their alloys, were changed of a significant way by the introduction of heavy interstitial elements. These interstitial elements (oxygen, for example) present in the metallic matrix occupy octahedral sites and constitute an elastic dipole of tetragonal symmetry and might produce anelastic relaxation. Polycrystalline samples of Nb–0.3wt%Ti (Nb–Ti) alloy with oxygen in solid solution were analysed. The anelastic spectroscopy measurements had been made in a torsion pendulum, with frequencies in the Hz range, at 300 to 700K. The results showed thermally activated relaxation structures were identified 4 relaxation process attributed to stress-induced ordering of single O, N and C atoms around niobium and stress-induced ordering of single O atoms around Ti atoms.

Stress-Induced Ordering Due to Heavy Interstitial Atoms in Nb–0.3wt%Ti Alloys. T.C.Niemeyer, C.R.Grandini, O.Florêncio: Materials Science and Engineering A, 2005, 396[1-2], 285-9