The effects of microstructure on the hydriding for 500 °C/2 h aged U-13at.%Nb alloy

Ji, Hefei; Chen, Xianglin; Shi, Pengjun; Hu, Guichao; Li, Ruiwen; Yang, Jiangrong; Wang, Xiaolin

doi:10.1016/j.jnucmat.2017.03.014

Cited by 13 publications

(6 citation statements)

References 25 publications

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“…7, the surface potential fluctuations are obvious, the maximum potential contrast was approximately 400 mV, which is sufficient to distinguish different regions by the surface potential distribution. Greater corrosion occurs in a lower-potential area 19,[22][23][24][25] ; thus, the fluctuating surface potentials indicate areas with different levels of corrosion resistance. From Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Details of the experimental procedure are described elsewhere. 19 The chamber was heated to 160°C under dynamic vacuum for 1 h for corrosion acceleration, so as to acquire H-attacked areas in a relatively short time. 34 The post-hydriding U-sample surface morphology was acquired using a LSCM.…”

Section: Methodsmentioning

confidence: 99%

“…Based on the above findings, it has been universally concluded that some particular positions on or in the U nearsurface region can be investigated as initial nucleation sites, with the aim of determining the hydriding characteristics. Previous results 11,[17][18][19] also indicate that hydride nucleates at the α-U-U 2 Ti boundary, and that H reacts preferentially with α-U. With regards to the nucleation and growth stage, Hill et al 13 and Scott et al 20 have found the phenomenon of hydride expansion in a particular direction (i.e., twinning).…”

Section: Introductionmentioning

confidence: 94%

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Mechanism of surface uranium hydride formation during corrosion of uranium

Pan

et al. 2019

npj Mater Degrad

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Uranium is widely used in the nuclear industry and it is well known that uranium hydride, UH 3 , forms when uranium is exposed to air. The associated volume change during this transition can cause the surface region to crack, compromising structural integrity. Here, hydriding regions beneath hydride surface craters are studied by secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). Our results indicate that strain transition regions exist, which are induced by hydrogen with a certain thickness between hydride craters and the uranium bulk. The SIMS and XPS results suggest that hydrogen exists covalently with uranium and oxygen in these transition regions. A micro-scale induction period model based on the transition region and previous hydriding models is developed. Within the so-called micro-scale induction period, hydrogen diffuses and accumulates at particular sites before reaching the critical concentration required to form stoichiometric UH 3 in the transition regions.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

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Mechanism of surface uranium hydride formation during corrosion of uranium

Pan

et al. 2019

npj Mater Degrad

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“…The hydriding experiments were performed in a homemade reaction system composed of a sealed furnace chamber containing a quartz glass window and a hot stage microscope system (HSM) for in situ monitoring. 35 The chamber temperature was raised to 160 °C for 30 min to activate the surface and then cooled down to a reaction temperature of 80 °C. The hydriding reaction was initiated with rapid pressurization of the reaction chamber with research-grade H 2 produced from heating up a LaNi 5 bed and terminated by evacuating the chamber after reaching a given exposure extent.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

What is the Role of Nb on Preferential Hydriding of Double-Phased Uranium, Stabilizing γ-U, or Avoiding Hydrogen Aggregation?

Wang

et al. 2021

J. Phys. Chem. C

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Uranium as the heaviest naturally occurring element plays important roles in nuclear industries. Hydrogen-caused corrosions and irradiation-caused structural damages are two critical degradations that threaten the safe storage and practical applications of uranium. Through alloying with transition metals like Nb, the γ-phase of U can be stabilized at room temperature, which shows better performance against hydrogen-caused corrosions than the ground-state α-U. The underlying mechanisms have not been fully understood yet. To explain the preferential hydriding phenomenon observed on a specially fabricated double-phase U-2.5 wt % Nb alloy, we perform multiscale ab initio calculations and kinetic Monte Carlo (KMC) simulations. We find that because of different diffusion mechanisms, intrinsic α-U and γ-U already show different hydrogen accumulation behaviors. The existence of random Nb atoms further inhibits hydrogen accumulation in γ-U. Our work declares its contribution by pointing out the important role of crystal lattice architectures on hydrogen accumulations in metals.

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Numerical simulation of microstructure evolution and microsegregation of U-Nb alloy during solidification process

Zhou

Deng

et al. 2017

China Foundry

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Male, born in 1985, Ph.D. His research interests mainly focus on multi-scale modeling and simulation of casting processes. Currently, he is paying much more attention to the microstructure simulation of uranium alloy. Abstract: In this work, a cellular automaton model has been developed to simulate the microstructure evolution of U-Nb alloy during the solidification process. The preferential growth orientation, solute redistribution in both liquid and solid, solid/liquid interface solute conservation, interface curvature and the growth anisotropy were considered in the model. The model was applied to simulate the dendrite growth and Nb microsegregation behavior of U-5.5Nb alloy during solidification, and the predicted results showed a reasonable agreement with the experimental results. The effects of cooling rates on the solidification microstructure and composition distribution of U-5.5Nb were investigated by using the developed model. The results show that with the increase of the cooling rate, the average grain size decreases and the Nb microsegregation increases. https://doi.org/10.1007/s41230-017-7135-6 U -Nb alloy, which exhibits many advantages such as special nuclear properties and high density, is widely used in the national defense and nuclear energy engineering field [1][2][3][4][5] . Since the density of two elements varies greatly and diffusion of Nb in uranium is particularly sluggish, microsegregation forms after solidification [5] , and it is difficult to eliminate them in subsequent heat treatment process. Therefore, it is of great significance to study of microstructure evolution and microsegregation behavior during the solidification process.U-Nb alloy is expensive and also radioactive, which limits the experimental research. In recent years, a variety of computer models, such as cellular automaton (CA) [6][7][8][9][10] , Monte Carlo [11] and phase field [12][13][14] , have been developed to simulate the microstructure evolution during the solidification process. CA method, as an efficient computational approach for microstructural simulation with a high computational efficiency, has been widely applied to the investigation of dendrite morphologies and microsegregation during metal solidification.In this work, a CA model has been developed to simulate the microstructure evolution of U-Nb alloy during solidification process. By using the model, microstructure evolution and Nb microsegregation behavior of U-5.5Nb alloy during solidification process were obtained, and an experiment was conducted for model validation. Then the model was applied to investigating the solidification microstructure and the composition distribution of U-5.5Nb under different cooling rates.

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The effects of microstructure on the hydriding for 500 °C/2 h aged U-13at.%Nb alloy

Cited by 13 publications

References 25 publications

Mechanism of surface uranium hydride formation during corrosion of uranium

Mechanism of surface uranium hydride formation during corrosion of uranium

What is the Role of Nb on Preferential Hydriding of Double-Phased Uranium, Stabilizing γ-U, or Avoiding Hydrogen Aggregation?

Numerical simulation of microstructure evolution and microsegregation of U-Nb alloy during solidification process

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