Development of a microstructural grand potential-based sintering model

Greenquist, Ian; Tonks, Michael; Aagesen, Larry K.; Zhang, Yongfeng

doi:10.1016/j.commatsci.2019.109288

Cited by 46 publications

(30 citation statements)

References 68 publications

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“…Yet, the simulations remain time-consuming, cf. [59]. An example simulations for 9 particles during 20 dimensionless time units took about 36 h, using 32 threads of the Threadripper 2990WX.…”

Section: Resultsmentioning

confidence: 99%

Multi-Scale Modelling of the Bound Metal Deposition Manufacturing of Ti6Al4V

Luchinsky

Hafiychuck

Wheeler

et al. 2022

Thermo

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Nonlinear shrinkage of the metal part during manufacturing by bound metal deposition, both on the ground and under microgravity, is considered. A multi-scale physics-based approach is developed to address the problem. It spans timescales from atomistic dynamics on the order of nanoseconds to full-part shrinkage on the order of hours. This approach enables estimation of the key parameters of the problem, including the widths of grain boundaries, the coefficient of surface diffusion, the initial redistribution of particles during the debinding stage, the evolution of the microstructure from round particles to densely-packed grains, the corresponding changes in the total and chemical free energies, and the sintering stress. The method has been used to predict shrinkage at the levels of two particles, of the filament cross-section, of the sub-model, and of the whole green, brown, and metal parts.

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Section: Resultsmentioning

confidence: 99%

Multi-Scale Modelling of the Bound Metal Deposition Manufacturing of Ti6Al4V

Luchinsky

Hafiychuck

Wheeler

et al. 2022

Thermo

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“…To restrict diffusion along the interfaces, all aforementioned works have considered a scalar mobility function. Greenquist et al [76,77] have also developed a grand potential-based sintering model, in conjunction with a tensorial mobility approach.…”

Section: Coupled Second-order Conservative and Nonconservative Equationsmentioning

confidence: 99%

Multiphase-field model for surface diffusion and attachment kinetics in the grand-potential framework

et al. 2021

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Grand-potential based multiphase-field model is extended to include surface diffusion. Diffusion is elevated in the interface through a scalar degenerate term. In contrast to the classical Cahn-Hilliard-based formulations, the present model circumvents the related difficulties in restricting diffusion solely to the interface by combining two second-order equations, an Allen-Cahn-type equation for the phase field supplemented with an obstacletype potential and a conservative diffusion equation for the chemical potential or composition evolution. The sharp interface limiting behavior of the model is deduced by means of asymptotic analysis. A combination of surface diffusion and finite attachment kinetics is retrieved as the governing law. Infinite attachment kinetics can be achieved through a minor modification of the model, and with a slight change in the interpretation, the same model handles the cases of pure substances and alloys. Relations between model parameters and physical properties are obtained which allow one to quantitatively interpret simulation results. An extensive study of thermal grooving is conducted to validate the model based on existing theories. The results show good agreement with the theoretical sharp-interface solutions. The obviation of fourth-order derivatives and the usage of the obstacle potential make the model computationally cost-effective.

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“…The model is capable of capturing the evolution of multiple phases, grains, and chemical species concurrently. It has previously been applied to model phase separation, solidification, and sintering of complex alloy systems [10,11,12,13]. Recently, Aagesen et al [14,15] applied the model to evaluate the bubble evolution in various nuclear materials.…”

Section: Phase-field Model Formulationmentioning

confidence: 99%

BISON microstructure-based pulverization criterion in high burnup structure

Aagesen

Biswas

Jiang

et al. 2021

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To improve the economics of commercial nuclear power production, utilities are seeking to increase the allowable burnup limit of UO 2 fuel. One of the main factors that contributes to the current burnup limit of 62 GWd/MTU in commercial light-water reactors (LWRs) is the risk of fine fragmentation or pulverization during a loss of coolant accident (LOCA). Pulverization primarily occurs at high burnups, especially when the high-burnup structure (HBS) has formed. To allow the industry to pursue increased burnup and develop mitigation strategies, it is essential to have improved capability to predict the onset of pulverization. However, the mechanism of pulverization is not well understood, and the existing predictive capabilities implemented in the BISON fuel performance code are empirical in nature.In this report, mesoscale simulations are used to improve understanding of the formation mechanism of the HBS and how it responds during a LOCA transient, and inform development of a BISON pulverization criterion. A phase-field model was used to simulate the evolution of bubble pressure as a result of HBS formation. The simulations showed that gas atoms diffuse from grain interiors to the new grain boundaries created during HBS formation and diffuse rapidly along these grain boundaries to reach existing bubbles. This causes an increase in bubble pressure in existing bubbles, leading to bubble growth during steady-state operation. To simulate the response of HBS bubbles to a LOCA transient, a newly developed phase-field model was used; in agreement with preliminary results from Fiscal Year 2020, bubble size did not change significantly during the duration of the transient. A phase-field fracture model was used to study fragmentation patterns in the HBS. Phase-field fracture simulations were used to determine a pulverization criterion for BISON. A function for the critical pressure for pulverization to occur was fit to data from the phase-field fracture simulations, and this function was implemented as a material property in BISON. For comparison, an analytical criterion for pulverization was developed and implemented within the same material property.

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Development of a microstructural grand potential-based sintering model

Cited by 46 publications

References 68 publications

Multi-Scale Modelling of the Bound Metal Deposition Manufacturing of Ti6Al4V

Multi-Scale Modelling of the Bound Metal Deposition Manufacturing of Ti6Al4V

Multiphase-field model for surface diffusion and attachment kinetics in the grand-potential framework

BISON microstructure-based pulverization criterion in high burnup structure

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