Anelastic relaxation due to Ti–H complexes in Nb–Ti alloys

Abstract

The internal-friction spectrum of the Nb–2 at.% Ti–H and Nb–5 at.% Ti–H systems has been investigated in the temperature range 60–300 K, exciting the flexural vibrations of the specimens at 20 kHz, for hydrogen concentrations varying between 0·15 and 4·2 at.%. Electrical resistivity and density measurements have also been performed in the specimens at room temperature. Two internal-friction peaks appear below 150 K, a well-pronounced peak and a secondary peak placed at a lower temperature. Increasing the hydrogen concentration has a dual effect on the main peak, a monotonic enhancement of its height and its shift towards lower temperatures down to a saturation value. The secondary peak presents similar features though its height and temperature shift appear to saturate more rapidly. A tentative model is proposed to explain the complex phenomenology of the relaxation maxima.