skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Calculations of hydrogen diffusivity in Zr-based alloys: Influence of alloying elements and effect of stress

Abstract

This report summarizes the progress on modeling hydrogen diffusivity in Zr-based alloys. The presence of hydrogen (H) can detrimentally affect the mechanical properties of many metals and alloys. To mitigate these detrimental effects requires fundamental understanding of the thermodynamics and kinetics governing H pickup and hydride formation. In this work, we focus on H diffusion in Zr-based alloys by studying the effects of alloying elements and stress, factors that have been shown to strongly affect H pickup and hydride formation in nuclear fuel claddings. A recently developed accelerated kinetic Monte Carlo method is used for the study. It is found that for the alloys considered here, H diffusivity depends weakly on composition, with negligible effect at high temperatures in the range of 600-1200 K. Therefore, the small variation in compositions of these alloys is likely not a major cause of the very different H pickup rates. In contrast, stress strongly affects H diffusivity. This effect needs to be considered for studying hydride formation and delayed hydride cracking.

Authors:
 [1];  [1];  [1]
  1. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
Research Org.:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1376196
Report Number(s):
INL/EXT-17-42435
TRN: US1800548
DOE Contract Number:
AC07-05ID14517
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; HYDROGEN; HYDRIDES; ALLOYS; CLADDING; METALS; MECHANICAL PROPERTIES; alloying elemen; hydrogen diffusivity; kinetic Monte Carlo; stress effect; Zr-based alloys

Citation Formats

Yu, J., Jiang, C., and Zhang, Y.. Calculations of hydrogen diffusivity in Zr-based alloys: Influence of alloying elements and effect of stress. United States: N. p., 2017. Web. doi:10.2172/1376196.
Yu, J., Jiang, C., & Zhang, Y.. Calculations of hydrogen diffusivity in Zr-based alloys: Influence of alloying elements and effect of stress. United States. doi:10.2172/1376196.
Yu, J., Jiang, C., and Zhang, Y.. Thu . "Calculations of hydrogen diffusivity in Zr-based alloys: Influence of alloying elements and effect of stress". United States. doi:10.2172/1376196. https://www.osti.gov/servlets/purl/1376196.
@article{osti_1376196,
title = {Calculations of hydrogen diffusivity in Zr-based alloys: Influence of alloying elements and effect of stress},
author = {Yu, J. and Jiang, C. and Zhang, Y.},
abstractNote = {This report summarizes the progress on modeling hydrogen diffusivity in Zr-based alloys. The presence of hydrogen (H) can detrimentally affect the mechanical properties of many metals and alloys. To mitigate these detrimental effects requires fundamental understanding of the thermodynamics and kinetics governing H pickup and hydride formation. In this work, we focus on H diffusion in Zr-based alloys by studying the effects of alloying elements and stress, factors that have been shown to strongly affect H pickup and hydride formation in nuclear fuel claddings. A recently developed accelerated kinetic Monte Carlo method is used for the study. It is found that for the alloys considered here, H diffusivity depends weakly on composition, with negligible effect at high temperatures in the range of 600-1200 K. Therefore, the small variation in compositions of these alloys is likely not a major cause of the very different H pickup rates. In contrast, stress strongly affects H diffusivity. This effect needs to be considered for studying hydride formation and delayed hydride cracking.},
doi = {10.2172/1376196},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}

Technical Report:

Save / Share:
  • On the basis of the literature data and the current results, the mechanism of pitting corrosion of Al-alloys is proposed. An assumption is made that the transport of Cl- ions through defects in the passive film of aluminum an aluminum alloys is not a rate determining step in pitting. The pit development is controlled by the solubility of the oxidized alloying elements in acid solutions. A very good correlation was found between the pitting potential and the oxidized alloying elements for metastable Al-Cr, Al-Zr, Al-W, and Al-Zn alloys. We expect that the effect of oxidized alloying elements in other passivemore » alloys will be the same as in Al-alloys. To verify this hypothesis, susceptibility to pitting in the function of alloying elements in the binary alloys and the composition of the oxide film has to be measured. We propose studying Fe- and Ni-alloys produced by a sputtering deposition method. Using this method one-phaseous alloy can be obtained, even when the two metals are immiscible using conventional methods. Another advantage to studying sputtered alloys is to find new materials with superior resistance to localized corrosion.« less
  • On the basis of the literature data and the current results, the mechanism of pitting corrosion of Al-alloys is proposed. An assumption is made that the transport of Cl- ions through defects in the passive film of aluminum an aluminum alloys is not a rate determining step in pitting. The pit development is controlled by the solubility of the oxidized alloying elements in acid solutions. A very good correlation was found between the pitting potential and the oxidized alloying elements for metastable Al-Cr, Al-Zr, Al-W, and Al-Zn alloys. We expect that the effect of oxidized alloying elements in other passivemore » alloys will be the same as in Al-alloys. To verify this hypothesis, susceptibility to pitting in the function of alloying elements in the binary alloys and the composition of the oxide film has to be measured. We propose studying Fe- and Ni-alloys produced by a sputtering deposition method. Using this method one-phaseous alloy can be obtained, even when the two metals are immiscible using conventional methods. Another advantage to studying sputtered alloys is to find new materials with superior resistance to localized corrosion.« less
  • The development of new treatment technologies based on the reversible alloying for titanium alloys with hydrogen is of interest to researchers because of the possibility of efficient control of the. structure of the alloys and the combination of their technological (hydrogen plasticization and hydrogen-mechanical treatment) and operational (thermal-hydrogen treatment) properties. At present, these methods are well justified from the scientific point of view; their technological schemes and treatment modes are well developed for some commercial titanium alloys. However, the problem of the influence of hydrogen on the parameters of diffusion of alloying elements in alloys based on titanium is stillmore » unresolved. It was conjectured that the diffusion mobility of substitutional elements increases in the presence of hydrogen. As a result, {open_quotes}titanium-alloying element-hydrogen{close_quotes} systems should attain equilibrium much faster. However, the results of subsequent investigations did not corroborate this hypothesis. It was shown that hydrogen introduced in Ti-Zr alloys increases the diffusion activation energy of substitutional atoms in bcc structures. At the same time, hydrogen introduced in Ti-V model alloys and in VT23, VT6, and other commercial titanium alloys sharply decreases the first critical cooling rate, i.e., the rate at which diffusion processes are suppressed, and the original high-temperature phase either undergoes the martensite transformation or is fixed at normal temperatures without changes in its composition.« less
  • During the second year of this project, progress was made in the following areas concerned with the effect of alloying elements on the corrosion resistance of RSP Mg alloys: (1) development of the surface-reflection x-ray spectroscopic technique (ref1EXAFS) to carry out structural studies on the films on Mg alloys that control corrosion was completed and applied in measurements at the oxygen K-edge of surface films on high-purity Mg and AZ61 Mg alloys. The existence of magnesium hydroxide on these surfaces was found. (2) Electrochemical studies of the effect of A1, Zn, Ce, Nd, Y, Mn, Li, and Ca in melt-spunmore » Mg alloy ribbons on corrosion behavior were carried out. The corrosion rate decreased with increased percentage of A1 and small additions of Zn. It was found that rapid solidification improves the resistance of the alloy studied (AZ61) to localized C1/sup -/ attack. (3) Surface analytical studies found that only Li and Ca in the RSP Mg alloys have a tendency to be enriched in the films on these alloys. Hydroxides and carbonates were also found in the surface films along with oxides.« less