Hydrogen permeation in rapidly quenched amorphous and crystallized Nb20Ti40Ni40 alloy ribbons

Formation of an amorphous (a-) Nb20Ti40Ni40 alloy by rapid quenching and its crystallization behavior were investigated by X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. The B2-TiNi phase was firstly crystallized and the remaining amorphous (a-) phase subsequently decomposed into the bcc-(Nb, Ti) + B2–TiNi phases. The crystallized (c-) Nb20Ti40Ni40 samples obtained by annealing above 1173 K were ductile and insusceptible to hydrogen embrittlement between 598 and 673 K. Hydrogen permeability at 673 K (Φ673K) for the a- and c-Nb20Ti40Ni40 alloys were 8.1 × 10−9 and (3.0–4.8) × 10−9 mol H2/m/s/Pa0.5, respectively. Φ673K increased with the increase in the diameter of the bcc-(Nb, Ti) phase, although this led to poor resistance to hydrogen embrittlement. The lower hydrogen permeability of the c-Nb20Ti40Ni40 alloy was due to its lower hydrogen diffusivity. The present work demonstrated that rapid quenching and subsequent annealing are useful to prepare thermally stable Nb–TiNi hydrogen permeation alloy membranes.

Research highlights
► Wide and amorphous Nb20Ti40Ni40 alloy ribbons can be prepared by rapid quenching technique.
► Two-phase structure of bcc-(Nb, Ti) and B2–TiNi are formed after crystallization.
► Granular (Nb, Ti) phase precipitates in the TiNi matrix after crystallization.
► Both of amorphous and crystallized alloys are hydrogen permeable with resist to hydrogen embrittlement.