Effect of partial Ni substitution in V85Ni15 by Ti on microstructure, mechanical properties and hydrogen permeability of V-based BCC alloy membranes

• Published in: Materials research express 2020-06, Vol.7 (6), p.066505
• Main Authors: Jiang, Peng, Sun, Bolin, Wang, Haichuan, Peng, Guosheng, Ma, Yangzhou, Song, Guangsheng, Dolan, Michael
• Format: Article
• Language: English
• Subjects: alloy elements; alloy membranes; Alloying elements; Alloys; BCC metals; Binary alloys; Composition effects; Diffusion barriers; Diffusion coefficient; Elongation; First principles; Hydrogen; hydrogen permeability; Hydrogen permeation; Mechanical properties; Membranes; Microstructure; microstructures; Nickel compounds; Palladium base alloys; Penetration; Permeability; Shape memory alloys; Solid solutions; Solution strengthening; Ternary alloys; Titanium compounds; Ultimate tensile strength; Vanadium base alloys; vanadium-nickel-titanium
• ISSN: 2053-1591
• DOI: 10.1088/2053-1591/ab98ca

Vanadium-based alloy membranes with body-centred-cubic (BCC) structure are considered as one of the leading alternatives to Pd-based alloys for hydrogen separation applications due to their lower cost and higher permeability. As permeability and mechanical properties depend on what microstructure can be produced mainly by alloy composition under same processing conditions, the effect of alloy composition on microstructure, mechanical properties and hydrogen permeability has been investigated for the V85Ni15 and V85Ni10Ti5 (at%) alloys prepared by a same process route. All Ni atoms dissolve into the V-matrix to form a single highly supersaturated solid solution with dendritic segregation of Ni-solute atoms in the binary alloy. A part of Ni replacement with 5 at% Ti leads to the formation of small interdendritic phases NiTi and NiTi2 in addition to major phase of V-based solid solution. The mechanical property testing shows that the ultimate strength of the ternary alloy is higher than that of the binary alloy, but the elongation and rollability are lower due to a combination of solid solution hardening and particle strengthening effect. The addition of Ti can greatly increase permeability about 4 times greater than the binary alloy at a permeation testing of 400 °C. But the presence of small amounts of interdendritic compounds provides a barrier to hydrogen migration, resulting in a relatively lower hydrogen diffusion coefficient. In theory, the diffusivity and solubility of hydrogen atom in the presence of alloying element Ti is higher than that in the presence of alloying element Ni in vanadium. This is demonstrated using first principles calculation which further explains the mechanism of hydrogen permeation.