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 ...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-5.5 Nb 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-5.5 Nb 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.展开更多
The phase equilibria and thermodynamic properties of the U-Nb system were investigated through experiments and thermodynamic modeling.In the experiments,a series of samples with different content of Nb were prepared b...The phase equilibria and thermodynamic properties of the U-Nb system were investigated through experiments and thermodynamic modeling.In the experiments,a series of samples with different content of Nb were prepared by arc melting.The Nb content covers the entire composition range of the U-Nb binary system.After solidification,the samples were annealed and then analyzed by X-ray diffraction,scanning electron microscopy,energy dispersive X-ray spectroscopy,differential scanning calorimeter and neutron diffraction.The equilibrium phases,including γ1(U-rich bcc),αU,and γ2(U-depleted bcc),were determined in detail from the experimental characterization.The occurrence of the invariant reaction γ1→αU+γ2 was confirmed,and the reaction temperature and composition were accurately identified.Moreover,the experimental findings clarify the dispute between the Dwight and Terekhov theories regarding the phase region(i.e.,whether the phase region is αU+γ1 or βU+γ2).Furthermore,the U-Nb phase diagram was reassessed by incorporating the present experimental data and previously published reliable experimental data from the literature.A set of self-consistent thermodynamic parameters were developed using CALPHAD(Calculation of phase diagrams),and the calculations reasonably agree with the experimental observations.展开更多
The U-Nb alloy,as a kind of nuclear material with good corrosion resistance and mechanical properties,plays an important role in the nuclear industry.However,the experimental measurements and theoretical calculations ...The U-Nb alloy,as a kind of nuclear material with good corrosion resistance and mechanical properties,plays an important role in the nuclear industry.However,the experimental measurements and theoretical calculations of many parameters which are essential in describing the dynamical properties of this alloy melt,including density,diffusivity,and viscosity,have not been carried out yet.The lack of data on the dynamical properties of nuclear materials seriously hinders the high-performance nuclear materials from being developed and applied.In this work,the dynamical properties of the U-Nb alloy melt are systematically studied by means of ab initio molecular dynamics simulations and their corresponding mathematical models are established,thereby being able to rapidly calculate the densities,diffusion coefficients,viscosities,and their activation energies in the whole U-Nb liquid region.This work provides a new idea for investigating the dynamical properties of binary alloy melts,thereby promoting the development of melt research.展开更多
基金supported by the Science and Technology Development Foundation of Chinese Academy of Engineering Physics(Grant No.2015B0203031)the Science Challenge Program(Grant No.TZ20160040201)
文摘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-5.5 Nb 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-5.5 Nb 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.
基金This work was financially supported by the Science Challenge Project of China(No.TZ2016004)the National Natural Science Foundation of China(No.51701193)the National Key Research and Development Program(No.2016YFB0700404)。
文摘The phase equilibria and thermodynamic properties of the U-Nb system were investigated through experiments and thermodynamic modeling.In the experiments,a series of samples with different content of Nb were prepared by arc melting.The Nb content covers the entire composition range of the U-Nb binary system.After solidification,the samples were annealed and then analyzed by X-ray diffraction,scanning electron microscopy,energy dispersive X-ray spectroscopy,differential scanning calorimeter and neutron diffraction.The equilibrium phases,including γ1(U-rich bcc),αU,and γ2(U-depleted bcc),were determined in detail from the experimental characterization.The occurrence of the invariant reaction γ1→αU+γ2 was confirmed,and the reaction temperature and composition were accurately identified.Moreover,the experimental findings clarify the dispute between the Dwight and Terekhov theories regarding the phase region(i.e.,whether the phase region is αU+γ1 or βU+γ2).Furthermore,the U-Nb phase diagram was reassessed by incorporating the present experimental data and previously published reliable experimental data from the literature.A set of self-consistent thermodynamic parameters were developed using CALPHAD(Calculation of phase diagrams),and the calculations reasonably agree with the experimental observations.
基金Project supported by the Science Challenging Project,China(Grant No.TZ2016004)the National Natural Science Foundation of China(Grant No.51701193)。
文摘The U-Nb alloy,as a kind of nuclear material with good corrosion resistance and mechanical properties,plays an important role in the nuclear industry.However,the experimental measurements and theoretical calculations of many parameters which are essential in describing the dynamical properties of this alloy melt,including density,diffusivity,and viscosity,have not been carried out yet.The lack of data on the dynamical properties of nuclear materials seriously hinders the high-performance nuclear materials from being developed and applied.In this work,the dynamical properties of the U-Nb alloy melt are systematically studied by means of ab initio molecular dynamics simulations and their corresponding mathematical models are established,thereby being able to rapidly calculate the densities,diffusion coefficients,viscosities,and their activation energies in the whole U-Nb liquid region.This work provides a new idea for investigating the dynamical properties of binary alloy melts,thereby promoting the development of melt research.
