Diffusion of Hydrogen in Titanium-Vanadium Alloys

2005 ◽  
Vol 237-240 ◽  
pp. 340-345 ◽  
Author(s):  
Hans Jürgen Christ ◽  
S. Schroers ◽  
F.H.S. dos Santos
Keyword(s):  
Diffusion Coefficient ◽  
Titanium Alloys ◽  
Hydrogen Concentration ◽  
Hydrogen Diffusion ◽  
High Strength ◽  
Vanadium Concentration ◽  
Vanadium Alloys ◽  
High Hydrogen ◽  
Hydrogen Diffusion Coefficient ◽  
Diffusion Of Hydrogen

β–titanium alloys are very attractive materials for many applications because they combine low density, high strength and excellent corrosion resistance. The available data indicate a much higher hydrogen diffusion coefficient in β–titanium alloys as compared to α and α + β alloys. In order to predict the range of applicability of β–titanium alloys in environments, which release hydrogen, the hydrogen diffusion coefficient (DH) needs to be known quantitatively. In the framework of this study the value of DH was determinated on samples, which were electrochemically hydrogen charged. Long thin rods were used as samples and charged in such a way that high hydrogen concentrations were obtained in one half of the length of the specimens, while the other half was kept virtually unaffected. After charging, the rods were annealed enabling hydrogen to diffuse. Hydrogen concentration profiles were experimentally determined and evaluated on the basis of the Matano technique, in order to reveal any effect of concentration on DH. The experiments were carried out on β–titanium alloys of the binary Ti–V system. The concentration range of vanadium in the alloys studied was selected in such a way that it represents the compositions commonly found in commercial alloys. The results show that the effect of hydrogen concentration on DH is negligible and that DH increases with the vanadium concentration.

Influence of Phases Stability on the Hydrogen Diffusion Coefficient in Ti-6Al-4V

2020 ◽  
Vol 986 ◽  
pp. 33-40
Author(s):  
Mohammed Kasim Mohsun
Keyword(s):  
Heat Treatment ◽  
Diffusion Coefficient ◽  
Titanium Alloys ◽  
Hydrogen Diffusion ◽  
Volume Fraction ◽  
Substantial Effect ◽  
Diffusion Annealing ◽  
Hydrogen Treatment ◽  
Β Phase ◽  
Hydrogen Diffusion Coefficient

For a unique microstructure creation, thermo-hydrogen treatment (THT), using hydrogen as a temporary alloying element within the heat treatment, is applied. This advanced heat treatment requires reliable data about the hydrogen diffusion coefficient (DH) for understanding diffusion kinetics and its effect on the mechanical behavior of the resulted phases. In this research, three different homogeneous microstructures were established for the investigation using different homogenization parameters. After that, the concentration of hydrogen, charged in the half-length of thin titanium rods via electrochemical hydrogenation, is specified. Then, a diffusion annealing heat treatment was carried out at different temperatures, leading to hydrogen diffusion in the hydrogenated specimens. Furthermore, DH was systematically determined using two methods including the explicit finite difference method (EFDM) and Matano technique (MT). For this purpose, Abaqus software was employed for modeling the hydrogen gradient established in the specimens. Additionally, scanning electron microscopy (SEM) was used for the microstructure examination in order to specify the influence of different hydrogen concentrations on the hydrogenated specimens. The experimental outcomes reveal a substantial effect of the β phase stability and grains sizes of the β and α phases on the hydrogen diffusion. Correspondingly, the results confirm that DH was independent of the hydrogen concentration, and obeys an Arrhenius-type temperature dependence. Furthermore, hydrogen diffusion in the α+β titanium alloys Ti-6Al-4V was slower in comparison to the hydrogen diffusion in the metastable β titanium alloys Ti-10V-2Fe-3Al. In conclusion, it was observed that DH is influenced by the previously performed heat treatments that determine the resulted microstructure types, and a slight influence of the volume fraction of the α phase on DH was observed as well.

Influence of Beta Stability on Hydrogen Diffusion in Various Beta Titanium Alloys

2009 ◽  
Vol 289-292 ◽  
pp. 87-94
Author(s):  
Hans Jürgen Christ ◽  
Peter Schmidt
Keyword(s):  
Diffusion Coefficient ◽  
Titanium Alloys ◽  
Diffusion Coefficients ◽  
Hydrogen Diffusion ◽  
Alloying Element ◽  
Hydrogen Diffusion Coefficient ◽  
Commercial Titanium ◽  
Beta Titanium ◽  
Microstructure Examination ◽  
Beta Titanium Alloys

The prediction of the applicability range of beta titanium alloys in hydrogen containing environments and the systematic study of hydrogen effects on the microstructure during heat treatment require reliable information about the hydrogen diffusion coefficient DH in the respective titanium alloy. Up to now the little information available on hydrogen diffusivity in commercial titanium alloys indicates a higher hydrogen diffusion coefficient in beta titanium alloys as compared to alpha and alpha + beta titanium alloys. In the present study, the hydrogen diffusion coefficients were determined systematically by means of electrochemically charging the half length of thin titanium rods and subsequent annealing, thereby enabling hydrogen diffusion. The Matano technique was applied in order to identify any effect of hydrogen concentration on DH. The hydrogen diffusion coefficients determined were correlated with results from microstructure examination applying optical and electron microscopy. Since molybdenum and vanadium are the most important beta-stabilizing alloying elements, binary titanium alloys of the Ti–Mo and the Ti–V systems at various contents of the respective alloying element were systematically studied in addition to commerical beta titanium alloys. The results of the experiments revealed the strong effect of beta stability and phase composition on hydrogen diffusion.

scholarly journals Hydrogen Diffusion Coefficient, Hydrogen Solution Coefficient and Hydrogen Permeability of Nb-TiNi Eutectic Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 1131-1136
Author(s):  
Wei Liang Wang ◽  
Kazuhiro Ishikawa ◽  
Kiyoshi Aoki
Keyword(s):  
Diffusion Coefficient ◽  
Hydrogen Absorption ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeability ◽  
K Value ◽  
Hydrogen Flow ◽  
Hydrogen Diffusion Coefficient ◽  
High K ◽  
Pressure Region ◽  
The Difference

In general, hydrogen permeabilityΦ of the alloy membrane is expressed as the product of the hydrogen diffusion coefficient D and the hydrogen solution coefficient K. Therefore, to improve the hydrogen permeability efficiently, the values of K and D should be separately considered. In the present study, hydrogen absorption and permeation behaviors of the Nb19Ti40Ni41 alloy consisting of the eutectic phase are investigated by measuring pressure-composition-isotherm (PCI) and by the hydrogen flow method and compared with those of palladium. The hydrogen absorption in the Nb19Ti40Ni41 alloy does not obey the Sieverts’ law in the pressure region of 0-1.0MPa at 523K, but it shows linear relationship between the difference in the square root of hydrogen pressure and hydrogen content between 0.1 and 0.4MPa. Although the value of D for the Nb19Ti40Ni41 alloy is considerably lower than that of palladium, its high K value enhances the hydrogen permeability Φ. It is suggested that the enhancement of D by microstructural control for Nb19Ti40Ni41 alloy is effective for improvement of Φ.

Investigation of hydrogen diffusion behavior in 12Cr2Mo1R(H) steel by electrochemical tests and first-principles calculation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiang Qiu ◽  
Kun Zhang ◽  
Qin Kang ◽  
Yicheng Fan ◽  
Hongyu San ◽  
...  
Keyword(s):  
Activation Energy ◽  
Diffusion Coefficient ◽  
Hydrogen Atom ◽  
Hydrogen Embrittlement ◽  
First Principles ◽  
Hydrogen Diffusion ◽  
First Principles Calculations ◽  
Content Type ◽  
Diffusion Behavior ◽  
Hydrogen Diffusion Coefficient

Purpose This paper aims to study the mechanism of hydrogen embrittlement in 12Cr2Mo1R(H) steel, which will help to provide valuable information for the subsequent hydrogen embrittlement research of this kind of steel, so as to optimize the processing technology and take more appropriate measures to prevent hydrogen damage. Design/methodology/approach The hydrogen diffusion coefficient of 12Cr2Mo1R(H) steel was measured by the hydrogen permeation technique of double electrolytic cells. Moreover, the influence of hydrogen traps in the material and experimental temperature on hydrogen diffusion behavior was discussed. The first-principles calculations based on density functional theory were used to study the occupancy of H atoms in the bcc-Fe cell, the diffusion path and the interaction with vacancy defects. Findings The results revealed that the logarithm of the hydrogen diffusion coefficient of the material has a linear relationship with the reciprocal of temperature and the activation energy of hydrogen atom diffusion in 12Cr2Mo1R(H) steel is 23.47 kJ/mol. H atoms stably exist in the nearly octahedral interstices in the crystal cell with vacancies. In addition, the solution of Cr/Mo alloy atom does not change the lowest energy path of H atom, but increases the diffusion activation energy of hydrogen atom, thus hindering the diffusion of hydrogen atom. Cr/Mo and vacancy have a synergistic effect on inhibiting the diffusion of H atoms in α-Fe. Originality/value This article combines experiments with first-principles calculations to explore the diffusion behavior of hydrogen in 12Cr2Mo1R(H) steel from the macroscopic and microscopic perspectives, which will help to establish a calculation model with complex defects in the future.

Hydrogen Diffusion Coefficient during Hydrogen Permeation through Nb-Based Hydrogen Permeable Membranes

2009 ◽  
Vol 283-286 ◽  
pp. 225-230 ◽  
Author(s):  
Hiroshi Yukawa ◽  
G.X. Zhang ◽  
N. Watanabe ◽  
Masahiko Morinaga ◽  
T. Nambu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Diffusion Coefficient ◽  
High Temperature ◽  
Solid Solutions ◽  
Diffusion Coefficients ◽  
Hydrogen Diffusion ◽  
Hydrogen Permeation ◽  
Pure Niobium ◽  
Hydrogen Diffusion Coefficient

The hydrogen diffusion coefficients are investigated during the hydrogen permeation through Nb-based hydrogen permeable membranes at high temperature. It is found that the hydrogen diffusion coefficient for pure niobium under practical conditions is much lower than the reported values measured for dilute hydrogen solid solutions. Surprisingly, the hydrogen diffusion is found to be faster in Pd-Ag alloy with fcc crystal structure than in pure niobium with bcc crystal structure at 773K during the hydrogen permeation. It is also found that the addition of Ru or W into niobium increases the hydrogen diffusion coefficient under the practical conditions.

Diffusion and Effusion of Hydrogen in Microcrystalline Silicon

1997 ◽  
Vol 467 ◽  
Author(s):  
W. Beyer ◽  
P. Hapke ◽  
U. Zastrow
Keyword(s):  
Diffusion Coefficient ◽  
Infrared Absorption ◽  
Cyclotron Resonance ◽  
Hydrogen Diffusion ◽  
Electron Cyclotron Resonance ◽  
Microcrystalline Silicon ◽  
Hydrogen Diffusion Coefficient ◽  
Internal Surfaces ◽  
Substrate Temperatures ◽  
Hydrogen Effusion

ABSTRACTThe diffusion and effusion of hydrogen in hydrogenated microcrystalline silicon films deposited in an electron cyclotron resonance reactor were studied for various deposition temperatures Ts. For deposition temperatures below 250°C, hydrogen effusion is found to be dominated by desorption of hydrogen from internal surfaces followed by rapid out-diffusion of H2. Higher substrate temperatures result in an increased hydrogen stability suggesting the growth of a more compact material. For this latter type of samples, a hydrogen diffusion coefficient similar as in compact plasma-grown a-Si:H films is found despite a different predominant bonding of hydrogen according to infrared absorption.

Hydrogen Diffusivity and Solubility in Internally Oxidized Pd0.97Zr0.03 and Pd0.97Nb0.03 Alloys

2010 ◽  
Vol 297-301 ◽  
pp. 715-721
Author(s):  
E.R. Lagreca ◽  
Viviane M. Azambuja ◽  
Dílson S. dos Santos
Keyword(s):  
Diffusion Coefficient ◽  
Grain Boundaries ◽  
Hydrogen Pressure ◽  
Hydrogen Diffusion ◽  
Gas Permeation ◽  
Hydrogen Diffusivity ◽  
Sem Images ◽  
Conventional Furnace ◽  
Hydrogen Diffusion Coefficient ◽  
Preferential Segregation

Internally oxidized (I.O.) Pd0.97Zr0.03 and Pd0.97Nb0.03 alloys were submitted to gas permeation tests with temperatures in the range of 473-873 K. The internal oxidation was kept in a conventional furnace at 1073 K for 24 hours in air contact. The formation of nano-oxides, ZrO2 and Nb2O5, dispersed in the Pd matrix was observed. SEM images showed a preferential segregation of these oxides in the grain boundaries. It was observed that the diffusion coefficient in the sample containing Nb oxide was smaller than that in the Pd-Zr oxide. The effect of hydrogen pressure was investigated in the Pd-Nb samples. It was observed that the hydrogen diffusion coefficient increases with increasing the pressure. The hydrogen solubility is bigger for the Pd-Zr internally oxidized. This effect is attributed to the Zr nanoxides, which are smaller than Pd-Nb precipitates and then offer more interface for trapping the hydrogen.

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