ISSN 0036-0295, Russian Metallurgy (Metally), Vol. 2017, No. 7, pp. 569–575. © Pleiades Publishing, Ltd., 2017. Original Russian Text © I.I. Chernov, M.S. Stal’tsov, B.A. Kalin, I.A. Bogachev, L.Yu. Guseva, S.N. Korshunov, 2017, published in Metally, 2017, No. 4, pp. 36–42.
Effect of the Chemical Composition and the Structural and Phases States of Materials on Hydrogen Retention I. I. Chernova, *, M. S. Stal’tsova, B. A. Kalina, I. A. Bogacheva, L. Yu. Gusevaa, and S. N. Korshunovb aNational b
Research Nuclear University MEPhI, Moscow, Russia National Research Center Kurchatov Institute, Moscow, Russia *e-mail:
[email protected] Received January 18, 2017
Abstract⎯The results of investigation of the effect of chemical composition and structural and phase states of reactor steels and vanadium alloys on their capture and retention of hydrogen introduced into the materials in various ways are presented. It is shown that, in the case of identical conditions of hydrogen introduction, the amount of hydrogen captured by austenitic steels is substantially higher than that captured by ferritic/martensitic steels. At the same time, the EP450 ODS ferritic/martensitic steel dispersion-strengthened with nanosized yttrium oxide particles retains a substantially higher amount of hydrogen as compared to that retained in the EP450 matrix steel. The alloying of vanadium with tungsten, zirconium, and titanium leads to an increase in the amount of retained hydrogen. The effect of titanium content on hydrogen retention is found to be nonmonotonic; the phenomenon is explained from a physical view point. Keywords: reactor steels, vanadium alloys, alloying, hydrogen retention DOI: 10.1134/S0036029517070059
INTRODUCTION It is known that, at certain hydrogen contents, temperature, and strain state of material, hydrogen negatively affects the properties of a structural material, namely, decreases its elastic characteristics, ultimate strength, yield stress, fracture stress, plasticity (relative elongation and contraction), and fracture toughness and changes the fracture mode from ductile to brittle [1–4]. This phenomenon is known as hydrogen embrittlement. During operation of reactor structural materials, helium is formed along with hydrogen, which lead to the degradation of the physical and mechanical properties of materials. In this case, a negative synergistic effect is frequently evident [5–7]. The microstructure, impurity and alloying elements in materials and their phase state substantially affect the regularities of hydrogen capture, retention, and release [1, 8–11]. The aim of the present study is to find regularities of the effect of chemical composition and structural and phase states of reactor steels and vanadium alloys on the capture and retention of hydrogen. EXPERIMENTAL We studied martensitic/ferritic steels EP450, EP450 ODS (oxide dispersion strengthened), EP900, austenitic steels ChS68 and Kh18N10T (Table 1), and V–(0.5–10 wt %) Ti, V–4 wt % W, V–1 wt % Zr vana-
dium alloys. For an investigation, we used steel samples subjected to heat treatment under standard conditions. The EP450 ODS steel was prepared by sparkplasma sintering (SPS); the holding time during normalizing was increased to 3 h. Vanadium alloy samples were annealed at 1000°C for 2 h. Samples subjected to electropolishing were saturated with hydrogen in two regimes, namely, (1) saturation with hydrogen at 623 K for 2000 h at a pressure of 16.8 MPa using an autoclave and (2) irradiation with H+ ions (with the energy E = 25 keV to the fluence F = 5 × 1020 H+/m2 at Tirr = 293 K) and serially with He+ (E = 40 keV, Tirr = 293 and 923 K, F = 5 × 1020 H+/m2) and H+ (under above mentioned conditions) ions. Some samples were implanted with D3+ ions (E = 10 keV, T = 293 K, to the fluence F = 1 × 1021 D3+/m2). The regularities of hydrogen capture, retention, and release were studied by thermal desorption spectroscopy (TDS) during uniform heating at a rate of 2 K/s. The absolute hydrogen content in samples was determined by reduction melting technique using an RHEN-602 gas analyzer. RESULTS AND DISCUSSION In considering the negative effect of hydrogen on the properties of reactor structural materials in [1], it was noted that the formation, capture, and retention
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Table 1. Chemical compositions (wt %) of steels Steel EP450 EP450 ODS (HE) EP450 ODS (SPS) EP900 ChS68 Kh18N10T
С
Сr
Ni
Мn
Мо
Nb
Ti
V
В
Others
0.12 0.12 0.12 0.16 0.06 ≤0.08
13.0 13.0 13.0 12.0 16.3 18.0
≤0.3 ≤0.3 ≤0.3 0.6 14.8 10.0
0.6 0.6 0.6 – 1.6 1.5
2.0 2.0 2.0 0.8 2.2 –
0.3 0.3 0.3 0.3 – –
– – – — 0.35 0.4
0.2 0.2 0.2 0.3 0.2 –
0.004 0.004 0.004 0.006 0.004 –
– 0.3 Y2O3 1 and 0.3 Y2O3 1.2 Si – –
of hydrogen in them are of importance; these processes are mainly determined by the crystal structure type, chemical composition, and structural and phase states of materials. We measured hydrogen desorption spectra for steels in different states. Curves 1 and 2 in Fig. 1a indicate data for the matrix EP450 steel subjected to rolling and EP450 ODS steel with 0.3 wt % Y2O3, which JD, 1018 m–2 s–1
was prepared by hot extrusion (HE); Fig. 1b shows curves for (3) EP450 steel with 0.3 wt % Y2O3 prepared by SPS and (4) EP450 ODS steel with 1 wt % Y2O3, which was prepared by SPS. Figure 1c presents data for (5) EP450 SPS steel and (6) EP450 ODS steel with 0.3 wt % Y2O3, which was prepared by SPS. Data on the integral hydrogen accumulation in the aforementioned steels are given in Fig. 1d. JD, 1018 m–2 s–1
(a)
(b)
12
12
4
2 8
8
4
4
3
1 0 300 12
500
700
900
1100
1300
8 6
900
T, K
1100
(d)
6 4
4
0 300
700
8
6
2
500 QD, 1020 m–2
(с)
10
0 300
5
2
Y2O3, wt %: 1.0 0.3 –
0 500
700
900
1100
T, K
EP450, EP450 ODS (HE)
SPS, 80 MPa, 890°C
Fig. 1. (a–c) Thermal desorption spectra of hydrogen (JD is the deuterium desorption flow) for EP450 steel samples in different structural and phase states upon irradiation with D3+ ions with the energy E = 10 keV to a dose of 1025 D+/m2 at room temperature (for curves 1–6, see text) and (d) data on integral hydrogen accumulation QD for samples. RUSSIAN METALLURGY (METALLY)
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Table 2. Hydrogen content (determined with RHEN-602 gas analyzer) in EP900 ferritic/martensitic (bcc) and Kh18N10T austenitic (fcc) steels irradiated serially with He+ ions (E = 40 keV, Tirr = 573–923 K) to a dose of 5 × 1020 He+/m2 and H+ (E = 25 keV, Tirr = 293 K) to a dose of 5 × 1020 H+/m2 [13] Material EP900
Kh18N10T
Tirr with He+ ions, K No irradiation
Character of helium bubbles
[H], ×10–4 wt %
No bubbles
8.9 ± 0.4
573
He-vacancy complexes HemVn
14.0 ± 0.7
693
Smallest over-equilibrium
7.7 ± 0.4
773
Over-equilibrium
8.2 ± 0.4
923
Under-equilibrium
9.8 ± 0.5
No bubbles
8.3 ± 0.4
573
He-vacancy complexes HemVn
18.9 ± 0.9
693
Smallest over-equilibrium
20.5 ± 1.1
773
Over-equilibrium
23.4 ± 1.2
923
Under-equilibrium
38.8 ± 1.9
No irradiation
As is seen from Fig. 1a, the amount of hydrogen accumulated by ferritic/martensitic ODS (HE) steel (the integral accumulation is ~1021 m–2) is twice as much as that (~4.6 × 1020 m–2) accumulated by the rolled matrix steel. The hydrogen content (~5 × 1020 m–2) in the EP450 steel, which was prepared by SPS without Y2O3 addition, is 1.5 times lower than that in the rolled steel (Fig. 1d). The addition of Y2O3 substantially increases the hydrogen retention; in this case, the amount of hydrogen (~1021 m–2) accumulated in the ODS steel prepared by SPS with 1 wt % Y2O3 is substantially higher than that (~7 × 1020 m–2) in the steel with 0.3 wt % Y2O3. It is also seen (Fig. 1d) that the maximum amount of hydrogen is retained in the ODS steel prepared by HE. Thus, the structural and phase states of steel and the presence of disperse Y2O3 nanoparticles substantially affect the amount of hydrogen retained in the ferritic/martensitic steel. The measurements of the absolute hydrogen content in steels, which were performed by reducing melting in using the RHEN-602 analyzer, showed that the EP450 ODS steel prepared by HE contains the maximum hydrogen amount (the similar data were obtained by thermal desorption spectroscopy). The EP450, EP450 ODS (SPS), and ChS68 steels are characterized by substantially lower contents of accumulated hydrogen; however, its contents in the EP450 ODS (SPS) and ChS68 steels are 1.6 and 5.8 times higher than that in the EP450 steel, respectively. In particular, the hydrogen contents in samples of EP450 ferritic/martensitic steel prepared by different methods and in the ChS68 austenitic steel irradiated with H+ ions RUSSIAN METALLURGY (METALLY)
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(E = 40 keV, Tirr = 293 K) to a dose of 5 × 1020 H+/m2 are the following (×10–4 wt %): EP450 EP450 ODS (HE) EP450 ODS (SPS) ChS68 2.5 26.9 4.1 14.4
The obtained data on the hydrogen retention in ODS steels correspond to results obtained by other investigators for EUROFER-97 and ODS-EUROFER-97 steels subjected to electrolytic saturation with hydrogen [12]. However, a comparison of temperatures of peaks in TDS spectra indicates that the temperatures corresponding to the release of radiation-induced hydrogen (480–500 K, see Fig. 1) are higher than those (420– 430 K [12]) related to the diffusion-introduced hydrogen, since the lattice (or “irradiation”) hydrogen is present in “deeper” traps as compared to those for diffusion mobile hydrogen [1]. Table 2 shows data on the hydrogen retention in the ferritic/martensitic EP900 and austenitic Kh18N10T steels subjected to serial irradiation with He+ and H+ ions. Note that the hydrogen contents in both steels irradiated with only H+ ions are approximately equal. He-vacancy complexes in bcc steel are traps for hydrogen, and helium bubbles formed at high temperatures are less efficient traps for hydrogen. The hydrogen content in the fcc steel continuously increases with decreasing pressure in helium bubbles (as bigger bubbles are formed with increasing He+ ion irradiation temperature (Tirr), and the maximum hydrogen amount is captured with big under-equilibrium bubbles when p < 2γ/r, where p is the gas pressure in a bubble, γ is the surface tension; r is the bubble radius [13].
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J, at H/(g s) II 8
I
5
4
6
H, 1020 at %/g
Ti, wt %: 1 0 2 0.5 3 1.0 4 5.0 5 10.0 6 5.0 Fe
(a)
5
8
4 6 3
3
4
at H/аt V, %
4 2
2
2
1 1
0 300
500
700
6
2 900
1100
0
0 H, wt %
T, K
(b)
0.16 Fig. 2. Hydrogen thermal desorption spectra for (1) vanadium and its alloys with (2–5) titanium and (6) iron, which were saturated with hydrogen in an autoclave (uniform heating rate is 2 K/s); I and II are gas release peaks and J is the hydrogen desorption flow.
0.12 0.08
The TDS curves for V–Ti alloys saturated with hydrogen in an autoclave show two peaks (Fig. 2); these are the low-temperature peak (I) at 780–790 K (its height depends on the alloy composition and its temperature position is independent on the composition) and the high-temperature peak (II) at 870– 880 K (its intensity and temperature position are determined by the alloy composition). The peak intensity changes as the titanium content increases. A titanium content of 0.5 wt % weakly affects the relationship of intensities of peaks I and II. For the alloy with 1 wt % Ti, an increase in the intensity of peak I and a decrease in the intensity of peak II are observed. As the Ti content increases to 5 and 10 wt %, the height of peak I decreases, whereas the height of peak II increases; this effect becomes more substantial as the titanium content increases from 5 to 10 wt %. Thus, we can conclude that the effect of titanium on the intensity of thermal desorption peaks and position of peak II is nonmonotonic. The presence of two gas-release peaks in the TDS curves indicates the existence of two kinds of traps for hydrogen introduced into samples in the autoclave without radiation damage of the structure. Since the temperature position of peak I is independent of the chemical composition of material, defects, the binding energy of which with hydrogen and their hydrogen capacity are independent of the presence of alloying elements in the solid solution, are traps for hydrogen at 780–790 K. Since vanadium hydrides are dissolved at a temperature from ~270 K [14], traps can be represented by thermal vacancies [15], dislocations, grain and twin boundaries, discontinuities, and other inher-
0.04
0
2
4
6
8 Ti, wt %
Fig. 3. Dependences of amount of hydrogen on the titanium content in V–Ti alloys determined by (a) thermal desorption spectroscopy and (b) with RHEN-602 gas analyzer.
ited defects, which have positive binding energy (eV) with hydrogen [16]: Н—V H—Vm (m > 4)
0.45–0.53 0.71–0.90
Н—dislocation Н—pore Н—helium bubble
0.24–0.62 0.78 0.75–0.78
The fact that the intensity (height) of peal I depends on the titanium content can indicate the effect of titanium atoms on the content of traps of this kind and/or the energy of their binding with hydrogen atoms. Traps of the second kind are the more efficient for hydrogen. In this case, both the intensity and temperature position of peak II are determined by the titanium content, and the effect of titanium content on them and the effect on the amount of retained hydrogen as well (Fig. 3) are nonmonotonic. We may assume that, along with traps of the first kind, hydrogen is retained in titanium hydrides, complex Ti1 – xVxHy hydrides, or γ TiH2 hydrides, since the standard enthalpy of forma-
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Table 3. Hydrogen content (determined with the RHEN-602 gas analyzer) in vanadium and V–Ti alloys Hydrogen content ([H], ppm) upon irradiation Material V V–0.5 wt % Ti V–l wt % Ti V–5 wt %Ti V–10 wt % Ti
H+
He+ (293 К) + Н+ (293 К) 13 ± 2 ⇒ 4.0 ± 0.8 ⇒ 16 ± 3 ⇒ 20 ± 4 ⇒ 1±4⇒
11 ± 2 2.0 ± 0.4 12 ± 2 16 ± 3 14 ± 3
tion of titanium hydride (–144.4 kJ/mol) is substantially lower than that of vanadium hydrides (‒39.9 kJ/mol) [17, 18]; the temperature of γ-hydride decomposition (~870 K [14]) coincides with that of peak II. The data given in Fig. 3 also indicate that the content of retained hydrogen in the alloy with 0.5 wt % Ti is 3 times lower than that in vanadium. At the same time, in the case of alloy with 1 wt % Ti, the amount of retained hydrogen is restored; at 5 wt % Ti, the hydrogen content is maximal. For the alloy with 10 wt % Ti, the amount of retained hydrogen decreases. In this case, the dependence of absolute retained-hydrogen content (determined by RHEN-602 gas-analyzer) on the titanium content in the alloy coincides with that determined by TDS. In the case of titanium content of 0.5 wt % (0.53 at %), titanium does not participate in the formation of hydrides and fixes oxygen and nitrogen, the total content of which in vanadium is 0.58 at %, since the standard enthalpy of formation of γTiH2 hydride is substantially (several times) higher and the entropy of formation is lower than those for titanium oxides and nitrides [19]. As the titanium content increases to 1 and 5 wt %, the amount of retained hydrogen again increases, since only part of titanium participates in the formation of oxides and nitrides; the rest of titanium is used for the formation of hydrides, which decompose at ~870 K. At a titanium content of ~10 wt %, part of titanium electron density is taken by vanadium [20]. Therefore, a decrease in the electron density of titanium atoms leads to a decrease in the amount of formed titanium hydrides and to the decrease in the content of hydrogen retained in the V–10 at % Ti alloy. Similar regularities of variations of the hydrogen retaining as functions of the titanium and vanadium contents are also observed in the case of ion-hydrogen introduction; the minimum hydrogen content is observed for the V–0.5 wt % Ti alloy. The maximum hydrogen content is detected for the V–5 wt % Ti alloy whatever the alloy was irradiated with H+ ions or preliminarily with He+ ions at different temperatures (Table 3). The preliminary irradiation with He+ ions at 293 K favors an increase in the amount of retained hydrogen; the formation of helium porosity by irradiRUSSIAN METALLURGY (METALLY)
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16 ± 3 9±2 18 ± 4 29 ± 6 20 ± 4
ation with He+ ions at 923 K leads to the further increase in retained hydrogen (the increase is shown by arrows in Table 3). In contrast to the diffusion saturation with hydrogen in an autoclave (see Fig. 2), the introduction of hydrogen ions is characterized by the absence of a lowtemperature peak at ~785 K (Fig. 4) and the presence of high-temperature peaks in a temperature range of 880–1090 K (Table 4). The calculations of the area under the TDS curve show that, in the case of irradiation with He+ + H+ ions, the content of hydrogen H, arb. units (a) 4 3
2
2 1
0 10 (b) 8 6 6 5
4
4
2 0 300
500
700
900
1100
T, K
Fig. 4. (a, b) Thermal desorption spectra of hydrogen for (1, 4) vanadium (He+ + H+) and vanadium alloys (2, 3) V–4 wt % W (implantation of H+ and He+ + H+, respectively), (5, 6) V–1 wt % Zr (H+ and He+ + H+, respectively); helium was implanted at 923 K.
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Table 4. Temperatures (K) of the peaks corresponding to the thermal desorption of hydrogen in vanadium and its alloys saturated with hydrogen by different techniques Peak
V
I II III IV
V–4 wt % W Autoclave saturation – – – –
785 ± 5 875 ± 5 – –
V–l wt % Ti
V–l wt % Zr
785 ± 5 875 ± 5 – –
– – – –
Ion irradiation Peak I II III IV
Н+
Не+ + Н+
– – – –
– 880 ± 10 – 1050 ± 10
Н+ – 850 ± 10 900 ± 10 1070 ± 10
Не+ + Н+
–
–
– 860 ± 10 940 ± 10 1090 ± 10
– – – –
– – – –
retained in vanadium V–4 wt % W and V–1 wt % Zr alloys is 1.4 and 2.2 times higher than that in vanadium, respectively. Thus, as in steels, the desorption temperature of hydrogen irradiation-introduced in vanadium alloys is higher than that of hydrogen introduced in an autoclave. CONCLUSIONS (1) It was shown that the amount of hydrogen trapped and held in oxide dispersion strengthened (ODS) steels is substantially higher than that in the matrix EP450 steel; an increase in the Y2O3 content in steel leads to an increase in the amount of retained hydrogen. (2) It was show that the amount of retained hydrogen substantially depends on the crystal structure type of material; under the same conditions of hydrogen introduction, the amount of hydrogen accumulated in austenitic steels is substantially higher than that accumulated in ferritic/martensitic steels. (3) It was found that the helium bubbles preliminarily formed in the austenitic steel are efficient hydrogen traps; as the pressure in bubbles decreases (i.e., as the bubble size increases), the amount of retained hydrogen increases. Helium pores in ferritic/martensitic steel become less efficient for retaining hydrogen. (4) It was noted that the alloying of vanadium with tungsten, zirconium, and titanium increases the amount of retained hydrogen introduced in alloys by ion irradiation. (5) It was found that the titanium content in vanadium nonmonotonically affects the retaining of hydrogen introduced both in an autoclave and by ion implantation. The hydrogen amount retained in an alloy with 0.5 wt % Ti is minimal; the hydrogen amount retained in an alloy with 5 wt % Ti is maximal. The
н+ – 850 ± 10 – 1050 ± 10
Не++ Н+ – 860 ± 10 905 ± 10 1050 ± 10
hydrogen amount retained in an alloy with 10 wt % Ti again decreases. This nonmonotonic dependence of retained hydrogen on the titanium content was explained from a physical viewpoint. (6) It was found that the desorption temperatures of irradiation-introduced hydrogen (lattice hydrogen) are higher than those of hydrogen introduced in an autoclave without irradiation damage of a structure (diffusion-mobile hydrogen). ACKNOWLEDGMENTS We thank the staff of Plasma Physics department, Professor A.A. Pisarev, associate professor Yu.M. Gasparyan, and engineer V.S. Efimov, for the assistance in performing the thermal desorption experiments. This study was supported by the Ministry of Education and Science of the Russian Federation in terms of the Competitiveness Improvement Program for the National Research Nuclear University MEPhI (contract no. 02.a03.21.0005) and was presented in the 13 International School–Conference on New Materials—Materials Life: Aging and Degradation of Materials during Operation of Nuclear Energy Installations (Moscow, October 17–21, 2016). REFERENCES 1. I. I. Chernov, M. S. Stal’tsov, B. A. Kalin, and L. Yu. Guseva, “Some problems of hydrogen in reactor structural materials,” Perspektivnye materialy, No. 4, 5–15 (2017). 2. B. A. Kalin, P. A. Platonov, Yu. V. Tuzov, et al., Physical Materials Science: Handbook for Higher Education. Vol. 6, Structural Materials for Nuclear Technology, Ed. by B. A. Kalin, (Izd. NIYaU MIFI, Moscow, 2012). 3. J. Koutský and J. Kocik, Radiation Damage of Structural Materials (Elsevier, Amsterdam, 2013).
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EFFECT OF THE CHEMICAL COMPOSITION AND THE STRUCTURAL AND PHASES STATES 4. G. N. Kasatkin, Hydrogen in Structural Steels (Intermet Inzhiniring, Moscow, 2003). 5. O. V. Borodin, V. V. Bryk, A. S. Kalchenko, et al., “Synergistic effects of helium and hydrogen on selfion-induced swelling of austenitic 18Cr10NiTi stainless steel,” J. Nucl. Mater. 442, S817–S820 (2013). 6. N. Sekimura, T. Iwai, Y. Arai, et al., “Synergistic effect of hydrogen and helium on microstructural evolution in vanadium alloys by triple ion beam irradiation,” J. Nucl. Mater. 283–287, 224–228 (2000). 7. T. Tanaka, K. Oka, S. Ohnuki, et al., “Synergistic effect of helium and hydrogen for defect evolution under multi-ion irradiation of Fe–Cr ferritic alloys,” J. Nucl. Mater. 329–333, 294–298 (2004). 8. S. Ohnuki, Y. Yasuda, T. Suda, et al., “Effect of alloying elements and neutron-irradiation on hydrogen behavior in V alloys,” J. Nucl. Mater. 329, 481–485 (2004). 9. V. V. Bandurko, A. A. Pisarev, and I. I. Chernov, “Effect of carbon content in nickel and iron on the capture of ion-introduced deuterium,” Izv. Akad. Nauk SSSR, Ser. Fiz. 54 (7), 1311–1413 (1990). 10. B. A. Kalin, A. N. Kalashnikov, I. I. Chernov, and A. A. Shmakov, “Hydrogen problems in reactor materials,” in Proceedings of the 7th International School for Young Scientists on Interaction of Hydrogen Isotopes with Structural Materials, Zvenigorod, Russia, 2011 (FGUP RFYaTs-VNIIEF, Sarov, 2012), pp. 10–54. 11. K. Natesan and W. K. Soppet, “Performance of V–Cr– Ti alloys in a hydrogen environment,” J. Nucl. Mater. 283–287, 1316–1321 (2000). 12. Y. Yagodzinskyy, E. Malitskii, M. Ganchenkova, et al., “Hydrogen effects on tensile properties of EUROFER 97 and ODS-EUROFER steels,” J. Nucl. Mater. 444, 435–440 (2014).
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13. S. Yu. Binyukova, I. I. Chernov, B. A. Kalin, and Than Swe, “Effectiveness of helium bubbles as traps for hydrogen,” J. Nucl. Mater. 367–370, Part A, 500–504 (2007). 14. O. M. Barabash and Yu. N. Koval’, Crystal Structure of Metals and Alloys: Handbook (Naukova Dumka, Kiev, 1986). 15. L. J. Gui, Y. L. Liu, W. T. Wang, et al., “First-principles investigations on vacancy trapping behavior of hydrogen in vanadium,” J. Nucl. Mater. 442, S688–S693 (2013). 16. I. I. Chernov, B. A. Kalin, and M. S. Stal’tsov, “Peculiarities of hydrogen behavior in reactor materials,” in Proceedings of the 4th International Conference and 6th International School for Young Scientists on Interaction of Hydrogen Isotopes with Structural Materials (FGUP RFYaTs-VNIIEF, Sarov, 2012), pp. 109–112. 17. I. Barin, Thermochemical Data of Pure Substances (Wiley-VCH, 1997). 18. A. N. Golubkov and A. A. Yukhimchuk, “Equilibrium pressure of protium and deuterium over vanadium dihydride phase,” in Proceedings of NATO Advanced Research Workshop on Hydrogen Materials Science and Chemistry of Metal Hydrides (Kluwer Acad. Publ., 2002), pp. 255–264. 19. L. P. Ruzinov and B. S. Gulyanitskii, Equilibrium Transformation of Chemical Reaction (Metallurgiya, Moscow, 1975). 20. S. N. Votinov, V. P. Kolotushkin, and A. A. Parfenov, Atomic Science and Industry. http://bus.znate.ru/ docs/index-27154.html?page=3.
Translated by N. Kolchugina
