PSI - Issue 40

E.D. Kurbanova et al. / Procedia Structural Integrity 40 (2022) 251–257 Kurbanova E.D., Polukhin V.A./ / Structural Integrity Procedia 00 (2022) 000 – 000

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With partial crystallization, if the size of the growing grains does not go beyond the nanometer range (<100 nm), this improves the characteristics - permeability, diffusion, strength and thermal stability. Thus, amorphous and nanocrystalline membranes have higher limits of elastic deformation, thermoplasticity, wear and corrosion resistance, since they do not contain intercrystalline defects, which are usually formed in crystal structures with translational symmetry. When creating each new membrane composition, it is necessary to analyze - resistance to the formation of hydrides, plasticity, the ability to diffuse elements in the process of matrix structuring, hydrogen permeability and corrosion resistance Polukhin et al. (2019,2014), Yan et al. (2014), Jiang et al. (2020). Thus prepared ready-made samples of membrane alloys were tested for permeability and diffusion intensity and with an assessment of the released hydrogen, followed by observations (X-ray - XDR), Fig. 3, of changes in microstructures under the influence of hydrogen. According to the diagram, ternary alloys Nb – Ti – Ni are solid solutions with B2-TiNi and BCC (Nb, Ti) phases. In hydrogenated Nb-enriched solid solutions of composition Nb 39 Ti 31 Ni 30 , the eutectic phase {(Nb, Ti) + TiNi} and the primary phase (Nb, Ti), respectively, with concentrations of Nb 20.5 Ti 38.5 Ni 41 , but not at all concentrations of the Nb – Ti – Ni alloy hydrides are formed. Based on in-situ X ray (XRD) data, Figure 2, the structural changes during hydrogenation (0.5 MPa H2) in the niobium-enriched alloy Nb 68 Ti 17 Ni 15 were recorded Yan et al. (2014), Jiang et al. (2020) vol% of the eutectic phase Nb 20.5 Ti 38.5 Ni 41 , and 74 vol.% of the primary phases Nb 40 Ti 30 Ni 30 and Nb 83 Ti 13 Ni 4 , respectively {BCC- (Nb, Ti) + TiNi} + (Nb, Ti)} without the presence of hydride formation only due to the presence of the eutectic phase Nb 39 Ti 31 Ni 30 and also the preselected element concentrations. So the Nb 39 Ti 31 Ni 30 alloy is represented by eutectic phases {(Nb, Ti) + TiNi}, as well as by the primary phase (Nb, Ti) in the solid solution matrix. The maximum value of the permeability of this alloy [with the phases B2-TiNi and BCC- (Nb, Ti)] is Ф ~ 2.0 × 10 -8 (mol H 2 m -1 s -1 Pa -0.5 ) at a temperature of 673 K, Yan et al. (2014), which is comparatively higher than that of Pd alloys. In this case, partial replacement of Nb with 5 vol. % in these alloys, Mo enhances the resistance of the alloys to hydrogen embrittlement, slightly reducing the permeability to Ф ~ 3.13 × 10 8 (mol H 2 m -1 s -1 Pa -0.5 ) Liu et al. (2018), which is again almost 2 times higher than pure Pd at the same operating temperatures of 673 K.

Fig. 3. Diffraction patterns of samples of membrane alloys based on niobium: Nb 40 Ti 30 Ni 30 Ding et al. (2016) (a) and vanadium: V 85 Ni 10 Ti 5 (b) and V 85 Ni 15 , Jiang et al. (2020), Polukhin et al. (2014) (c).