Keywords and Phrases
Hydride; Phase Field
"Zirconium alloys are commonly used in nuclear fuel rod claddings due to their high ductility, good corrosion resistance, and low neutron absorption cross section. Among the most important weaknesses of zirconium alloys is their affinity for hydrogen, resulting in formation of hydrides in the cladding, and leading to embrittlement and mechanical failure. Despite numerous studies on hydride precipitation in zirconium alloys, the nucleation and formation path of stable δ hydrides in α zirconium matrix are not yet fully understood.
In this Ph.D. research project, two novel quantitative phase-field models were developed and utilized to advance our understanding of mechanisms of formation and evolution of hydrides in zirconium alloys. First, a phase-field model for unstable γ hydride precipitation was created to build on previous computational models by including the actual Gibbs free energy of formation of hydrides in the total free energy of the system. Results from isothermal simulations of seeded and random nucleation in single crystal α-zirconium matrix showed that the thickness of non-equilibrium hydrides varied with temperature during evolution, and the hydrides were more rod-like (thinner) at higher temperatures and thicker at lower temperatures. Quench simulations with random nucleation indicated that the majority of precipitation occurs at early stages of quenching, but the size and shape of hydrides change as the temperature decreases.
The most detrimental phase of hydrides in claddings is the stable δ phase. A multiphase model including the two metastable phases (ζ and γ) and the δ phase was created to determine the effects of the intermediate phases on the nucleation and morphology of δ hydrides. Results from simulations both with and without applied strains indicated that the intermediate phases are influential in the initial formation and evolution of δ hydrides"--Abstract, page iv.
Asle Zaeem, Mohsen
Van Aken, David C.
Materials Science and Engineering
Ph. D. in Materials Science and Engineering
Idaho National Laboratory
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- A review on hydride precipitation in zirconium alloys
- A phase-field model to study the effects of temperature change on nucleation and growth of γ-hydrides in zirconium
- Formation path of δ hydrides in zirconium by multiphase field modeling
- Effects of external stresses on formation and shape evolution of zirconium hydrides by a multiphase field model
xi, 121 pages
© Jacob Luke Bair
Dissertation - Open Access
Library of Congress Subject Headings
Phase transformations (Statistical physics)
Nuclear fuel claddings -- Analysis
Electronic OCLC #
Bair, Jacob Luke, "Multiphase field modeling of the formation path of delta hydrides in zirconium" (2016). Doctoral Dissertations. 2527.