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 ( Φ 673 K ) 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. Φ 673 K 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.