抄録
The alloying effects on the stability of vanadium hydrides have been investigated systematically for binary V–M and ternary V–Ti–M alloys, where M’s are various alloying elements. The PCT curves for the β phase (V2H or VH) are measured at low hydrogen pressures using an electrochemical method. On the other hand, for the γ phase (VH2), the PCT curves are measured at high hydrogen pressures using an ordinary Sieverts-type apparatus. It is found that the phase stability of vanadium hydrides is affected strongly by the presence of a small amount of elements added to vanadium metal. The alloying effects on the hydride stability are different between the γ phase and the β phase. For example, the γ phase becomes most unstable when the group 8 elements in the periodic table, Fe, Ru and Os, are added to vanadium metal. On the other hand, the stability of the β phase changes monotonously following the order of elements in the periodic table. Also, the efficiency of alloying element in modifying the hydride stability is found to be different between the β1 phase (V2H) and the β2 phase (VH). In addition, it is shown that the logarithm of the plateau pressures for the β1 and the γ phases change almost linearly with the amount of alloying element in the alloy. Using this linear relationship for the γ phase, the second plateau pressures of ternary V–Ti–Ru and V–Ti–Cr alloys can be estimated quantitatively in the wide compositional range.
