Investigation of Mechanical, Thermal, Electrical, and Hydrogen Diffusion Properties in Ternary V–Ti–X Alloys: A Density Functional Theory Study

Abstract

The effects of alloying and hydrogen dissolution on the mechanical, thermal, and electrical properties of vanadiumbased ternary alloys were investigated using density functional theory. Our study showed that pure V has a lower solution energy than V−Ti−X alloys. Also, tetrahedral interstitial sites are more favorable than octahedral sites to be occupied by the H atoms. Furthermore, the alloys with eight H atoms have a lower capacity than the pure V system for H-trapping at interstitial sites. These findings suggest that H-dissolution in alloys is less probable than in pure V, and the alloys are more resistant to hydrogen embrittlement, crack propagation, and fracture initiation. Indeed, V−Ti−Al shows a reliable performance and could be a viable non-Pd alloy for hydrogen separation. Studying the mechanical properties of pure V and the ternary alloys revealed that V−Ti−Ni provides the highest durability and better resistance to both external and hydrogen dissolution-induced internal stresses. The V−Ti−Pd alloy has a higher diffusion barrier energy (E b = 0.1807 eV) than pure V (E b = 0.1646 eV), indicating that the H atom faces more hindrance when it diffuses across the alloy. Nonetheless, in the hydrogen separation temperature range, the V−Ti−Pd alloy has the largest thermal expansion coefficient (α = 2.048×10 −5 K −1 ), which indicates its poor thermal characteristics. Altogether, the superior mechanical properties of the V−Ti−Ni alloy indicate that it will be resistant to deformation and have a long service life in hydrogen separation applications. The V−Ti−Ni alloy has a higher heat capacity than the others, which is important in exothermic processes like hydrogen separation.