Abstract
Microstructures and hydrogen permeability (Φ) of as-cast Nb-Ti-Ni alloys have been investigated by scanning electron microscopy (SEM) and by the gas permeation technique, respectively. The Φ value increases with increasing temperature and the amount of the Nb content for every alloy. In these alloys, the Nb39Ti31Ni30 alloy, consisting of the primary bcc-(Nb, Ti) solid solution and the eutectic {(Nb, Ti)+TiNi} phase, shows the highest Φ, which is equivalent to that of Pd. On the other hand, the Nb10Ti50Ni40 alloy, consisting of the primary B2-TiNi compound and the eutectic {(Nb, Ti)+TiNi} phase, shows the lowest Φ value among the alloys for which Φ is measurable. Eutectic microstructures suppress the hydrogen embrittlement, while the primary (Nb, Ti) phase contributes to the hydrogen permeation in these alloys. The present work demonstrates that duplex alloys containing eutectic microstructures are promising for hydrogen permeation membranes with high resistance to the hydrogen embrittlement.
