On the terminal solubility of hydrogen in NbV alloys

The terminal solubility of hydrogen (TSH) in NbV alloys is extraordinarily high (at 250 K) in comparison to the TSH values in the component pure metals. An explantion is presented which involves using other thermodynamic data for the system and, where these are lacking, estimating them with the aid of physically reasonable assumptions. The hydrogen atoms, but not the metal atoms, are assumed to be in equilibrium between different phases and the hybride phase mixtures are assumed to be quasi-binary. It is shown that the high TSH results from the suppression of the α-α′ phase transition in the alloys, together with the fact thet there are larger deviations from ideal mixing in the hybride phase as compared with the metal phase.