Hydrogen permeation in rapidly quenched amorphous and crystallized Nb20Ti40Ni40 alloy ribbons

Hydrogen permeability and microstructure of rapidly quenched Nb–TiNi alloys

“…˚6 73 K of the amorphous Nb 20 Ti 40 Ni 40 alloy is almost same as the corresponding crystalline alloy [6][7][8]. The crystalline Nb 20 Ti 40 Ni 40 alloy obtained by crystallization of the amorphous alloy, consisted of the TiNi and the (Nb, Ti) phases, is ductile, but its ˚ is too low in comparison to that of pure Pd [6][7][8]. We have reported that ˚ of the arc melted Nb-TiNi alloys is improved in Nb-rich alloys, which is caused by the increase of the volume fraction of the (Nb, Ti) phase showing high ˚ [9].…”

“…The present authors have prepared the amorphous alloy ribbon by the rapid quenching of the eutectic crystalline Nb 20 Ti 40 Ni 40 alloy, and hydrogen permeability at 673 K, i.e. ˚6 73 K of the amorphous Nb 20 Ti 40 Ni 40 alloy is almost same as the corresponding crystalline alloy [6][7][8]. The crystalline Nb 20 Ti 40 Ni 40 alloy obtained by crystallization of the amorphous alloy, consisted of the TiNi and the (Nb, Ti) phases, is ductile, but its ˚ is too low in comparison to that of pure Pd [6][7][8].…”

Changes in microstructures and hydrogen permeability of Nb30Hf35Co35 eutectic alloy membranes by annealing

“…According to these models, the relationship between the microstructure and F (or D) of NbeTiNi/TiCo alloys has been investigated systematically by Saeki et al [21,22]. In the present case, when the continuous and discontinuous distributions of BCC-(Nb, Hf) and HfCo phases in as-cast and a-samples are analogized to the parallel and mixed microstructure, respectively, hydrogen permeability (Ф p and Ф m ) can be described as follow [8,14]:…”

“…Correspondingly, mechanical strain and defects are introduced in the deformed membranes which act as hydrogen trapping sites. A sequent annealing is thus needed to remove these defects, but in turn may induce microstructural changes [8]. Wang et al [10] investigated the microstructural change and its effect on hydrogen permeability in as-cast eutectic Nb 19 Ti 40 Ni 41 alloy by annealing, and found that the initial fully lamellar eutectic microstructure turned into a duplex phase by annealing at 1373 K for 168 h. Correspondingly, its hydrogen permeability at 573 K, F 573 K , is about one half of the as-cast state.…”

“…If this alloy exhibits a high F value compared to the eutectic Nb 30 Ti 35 Co 35 [11] and Nb 19 Ti 40 Ni 41 [10] alloys after annealing, then we may use the rapid quenching technique to prepare thin Nb-HfCo amorphous membrane. However, amorphous alloys are usually thermally unstable and their desirable properties may lost by crystallization under different annealing temperatures [8,14]. Accordingly, it is essential to research on the crystallization behaviors and microstructure stability by heat treatments under different temperatures.…”