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Effect of Central Multiphase Microstructure of Thick Plates on Work Hardening and Crack Propagation

Acta Metallurgica Sinica(English Letters) 2024年第2期37卷 325-338页

作者： Lei Hu Liqin Zhang Feng Hu Kuan Zheng Guohong Zhang Collaborative Innovation Center for Advanced Steels Wuhan University of Science and TechnologyWuhan430081China Department of Applied Physics Wuhan University of Science and TechnologyWuhan430081China Analysis and Testing Center Wuhan University of Science and TechnologyWuhan430081China

The effect of multiphase microstructure in the center segregation zones(CSZ)of high-strength steel thick plates on work hardening characteristics and crack initiation/propagation were *** was correlated with deformation damage behavior by using Taylor factor(TF)gradients,kernel average misorientation(KAM),and geometric necessary dislocation(GND)*** results show that the segregation leads to a mixed structure of ferrite(soft phase)and martensite/bainite(hard phase)in the center of the thick *** to the 1/4 thickness(1/4 T)region,grain refinement occurred in the CSZ,with KAM values increasing from 0.24 to 0.49 and a decrease in the proportion of high-angle grain boundaries(>15°)from 77.4 to 51.8%.In the process of deformation,due to the influence of grain refinement and adjacent martensite/bainite,ferrite grains were divided into structural units with different TF *** higher KAM value and GND density at the interface between soft/hard phases resulted in severe work *** addition,the presence of micron-sized inclusions in the CSZ caused local strain concentration and non-continuous deformation of the matrix,which induced crack *** fracture surface showed a mixed mode of brittle cleavage fracture and ductile fracture.

关键词： Thick plate center segregation zone Multiphase microstructure Taylor factor Crack propagation

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The High-Order Variable-Coefficient Explicit-Implicit-Null Method for Diffusion and Dispersion Equations

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应用数学与计算数学学报 2025年第1期7卷 115-150页

作者： Meiqi Tan Juan Cheng Chi-Wang Shu Graduate School China Academy of Engineering PhysicsBeijing 100088China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China HEDPS Center for Applied Physics and TechnologyCollege of EngineeringPeking UniversityBeijing 100871China Division of Applied Mathematics Brown UniversityProvidenceRI 02912USA

For the high-order diffusion and dispersion equations,the general practice of the explicit-implicit-null(EIN)method is to add and subtract an appropriately large linear highest derivative term with a constant coefficient at one side of the equation,and then apply the standard implicit-explicit method to the equivalent *** call this approach the con-stant-coefficient EIN method in this paper and hereafter denote it by"CC-EIN".To reduce the error in the CC-EIN method,the variable-coefficient explicit-implicit-null(VC-EIN)method,which is obtained by adding and subtracting a linear highest derivative term with a variable coefficient,is proposed and studied in this *** with the local discon-tinuous Galerkin(LDG)spatial discretization,the VC-EIN method is shown to be uncon-ditionally stable and can achieve high order of accuracy for both one-dimensional and two-dimensional quasi-linear and nonlinear *** addition,although the computational cost slightly increases,the VC-EIN method can obtain more accurate results than the CC-EIN method,if the diffusion coefficient or the dispersion coefficient has a few high and narrow bumps and the bumps only account for a small part of the whole computational domain.

关键词： Diffusion equation Dispersion equation Stability Explicit-implicit-null(EIN)time discretization Local discontinuous Galerkin(LDG)method

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Fragmentation dynamics of electron-impact double ionization of helium

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Chinese physics B 2023年第6期32卷 9-15页

作者：刘士炜叶地发刘杰 Beijing Computational Science Research Center Beijing 100193China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Graduate School China Academy of Engineering PhysicsBeijing 100193China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.

关键词： double ionization classical trajectory Monte Carlo simulation Wannier threshold law ergodicity

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First-principles study of structural and electronic properties of multiferroic oxide Mn_(3)TeO_(6) under high pressure

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Chinese physics B 2024年第7期33卷 448-454页

作者：潘小龙王豪柳雷陈向荣耿华运 College of Physics Sichuan UniversityChengdu 610065China National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsChina Academy of Engineering PhysicsMianyang 621900China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

Mn_(3)TeO_(6)(MTO) has been experimentally found to adopt a P2_(1)/In structure under high pressure,which exhibits a significantly smaller band gap compared to the atmospheric R3 *** this study,we systematically investigate the magnetism,structural phase transition,and electronic properties of MTO under high pressure through first-principles *** R3 and P2_(1)/n phases of MTO are antiferromagnetic at zero *** R3 phase transforms to the P2_(1)/n phase at 7.5 8 GPa,accompanied by a considerable volume collapse of about 6.47%.Employing the accurate method that combines DFT+U/and GW,the calculated band gap of R3 phase at zero pressure is very close to the experimental values,while that of the P2_(1)/n phase is significantly *** main reason for this difference is that the experimental study incorrectly used the Kubelka-Munk plot for the indirect band gap to obtain the band gap of the P2_(1)/n phase instead of the Kubelka-Munk plot for the direct band ***,our study reveals that the transition from the R3 phase to the P2_(1)/n phase is accompanied by a slight reduction in the band gap.

关键词： magnetism phase transition band gap high pressure

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A novel triple periodic minimal surface-like plate lattice and its data-driven optimization method for superior mechanical properties

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applied Mathematics and Mechanics(English Edition) 2024年第2期45卷 217-238页

作者： Yanda WANG Yanping LIAN Zhidong WANG Chunpeng WANG Daining FANG State Key Laboratory for Turbulence and Complex Systems&Center for Applied Physics and Technology College of EngineeringPeking UniversityBeijing 100871China Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing 100081China

Lattice structures can be designed to achieve unique mechanical properties and have attracted increasing attention for applications in high-end industrial equipment,along with the advances in additive manufacturing(AM)*** this work,a novel design of plate lattice structures described by a parametric model is proposed to enrich the design space of plate lattice structures with high connectivity suitable for AM *** parametric model takes the basic unit of the triple periodic minimal surface(TPMS)lattice as a skeleton and adopts a set of generation parameters to determine the plate lattice structure with different topologies,which takes the advantages of both plate lattices for superior specific mechanical properties and TPMS lattices for high connectivity,and therefore is referred to as a TPMS-like plate lattice(TLPL).Furthermore,a data-driven shape optimization method is proposed to optimize the TLPL structure for maximum mechanical properties with or without the isotropic *** this method,the genetic algorithm for the optimization is utilized for global search capability,and an artificial neural network(ANN)model for individual fitness estimation is integrated for high efficiency.A set of optimized TLPLs at different relative densities are experimentally validated by the selective laser melting(SLM)fabricated *** is confirmed that the optimized TLPLs could achieve elastic isotropy and have superior stiffness over other isotropic lattice structures.

关键词： lattice structure triple periodic minimal surface(TPMS) plate lattice structural optimization machine learning

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Fracture mechanism of inclusions in thick plate center under tensile loading

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Journal of Iron and Steel Research International 2024年第5期31卷 1196-1209页

作者： Lei Hu Li-qin Zhang Feng Hu Guo-hong Zhang Kuan Zheng Collaborative Innovation Center for Advanced Steels Wuhan University of Science and TechnologyWuhan430081HubeiChina Department of Applied Physics Wuhan University of Science and TechnologyWuhan430081HubeiChina Analysis and Testing Center Wuhan University of Science and TechnologyWuhan430081HubeiChina

Segregation of solute atoms in the center of thick plates of the tempered steel can cause an inhomogeneous structural transformation and generate micron-sized inclusions,which leads to lamellar tearing of thick plate and decreases the plasticity and *** formation and fragmentation mechanisms of micron-sized inclusions,like MnS and(Nb,Ti)C,in the center of thick plates were investigated by using thermodynamic calculations,finite element simulations,and electron backscatter diffraction characterization *** results show that micron-sized inclusions nucleate and grow in the liquid phase,and under tensile loading,they exhibit three fragmentation *** local stress during the fragmentation of inclusions is lower than the critical fracture stress of adjacent grains,and phase boundaries can effectively impede crack propagation into the *** existence of a low proportion of high-angle grain boundaries(58.1%)and high Kernel average misorientation value(0.534°)in the segregation band promotes inclusions fragmentation and crack *** difference in crack initiation and propagation direction caused by the morphology of inclusions and physical properties,as well as different matrix arrest abilities,is the main reasons for the diversity of inclusion fragmentation.

关键词： Thick plate Inclusion Finite element simulation Critical fracture stress Fracture mechanism

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Prediction of superionic state in LiH_(2) at conditions enroute to nuclear fusion

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Chinese physics B 2023年第10期32卷 566-571页

作者：李福德王豪李津龙耿华运 National Key Laboratory of Shock Wave and Detonation Physics Institute of Fluid PhysicsCAEPMianyang 621900China HEDPS Center for Applied Physics and Technologyand College of EngineeringPeking UniversityBeijing 100871China

Hydrogen and lithium,along with their compounds,are crucial materials for nuclear fusion ***-pressure studies have revealed intricate structural transitions in all these ***,research on lithium hydrides beyond LiH has mostly focused on the low-temperature ***,we use density functional theory and ab initio molecular dynamics simulations to investigate the behavior of LiH_(2),a hydrogen-rich compound,near its melting *** study is particularly relevant to the low-pressure region of the compression pathway of lithium hydrides toward *** discovered a premelting superionic phase transition in LiH_(2)that has significant implications for its mass transportation,elastic properties,and sound *** theoretical boundary for the superionic transition and melting temperature was then *** contrast,we also found that the primary compound of lithium hydrides,LiH,does not exhibit a superionic *** findings have important implications for optimizing the compression path to achieve the ignition condition in inertial confinement fusion research,especially when lithium tritium-deuteride(LiTD)is used as the fuel.

关键词： lithium polyhydrides high pressure and high temperature superionic state phase transition

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Quantitative method to predict the energetics of helium-nanocavities interactions in metal systems based on electrophobic interaction

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Journal of Materiomics 2024年第3期10卷 725-737页

作者： Fengping Luo Bowen Zhang Zhiying Gao Jia Huang Hong-Bo Zhou Guang-Hong Lu Fei Gao Yugang Wang Chenxu Wang State Key Laboratory of Nuclear Physics and Technology Center for Applied Physics and TechnologyPeking UniversityBeijing100871China Department of Physics Beihang UniversityBeijing100191China Department of Nuclear Engineering and Radiological Science University of MichiganAnn ArborMI48109USA

Energetics of helium-nanocavities interactions are crucial for unveiling underlying mechanisms of nanocavity evolution in nuclear ***,it becomes intractable and even not feasible to obtain these energetics via atomic simulations with increasing nanocavity size and increasing helium content in ***,a universal scaling law of helium-induced interaction energies in nanocavities in metal systems is proposed based on electrophobic interaction of *** on this scaling law and ab-initio calculations,a predictive method for binding energies of helium and displacement defects to nanocavities of arbitrary sizes and with different helium/vacancy ratios is established for BCC iron as a representative and validated by atomic *** predictive method reveals that the critical helium/vacancy ratio for helium-enhanced vacancy binding to nanocavities in-creases with increasing nanocavity size,and the helium/vacancy ratio giving the highest stability of nanocavities is about *** Ostwald ripening of nanocavities is delayed by helium to higher temper-atures due to reduced vacancy de-trapping rates from *** proposed scaling law can be generalized to many metal systems studied in the nuclear materials *** readily coupled into mesoscale models of irradiation damages,this predictive method facilitates clarifying helium role in cavity swelling of metallic nuclear materials.

关键词： Nanocavities Helium Electrophobic interaction Predictive method

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Different mechanisms of A-site and B-site high entropy effect on radiation tolerance of pyrochlores

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Journal of Materials Science & technology 2024年第24期191卷 250-258页

作者： Yuxin Li Yiming Lei Hao Xiao Shuang Zhao Yugang Wang Zini Cao Jie Zhang Jingyang Wang Guowei Lu Liuxuan Cao Chenxu Wang State Key Laboratory of Nuclear Physics and Technology Center for Applied Physics and TechnologyPeking UniversityBeijing 100871China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China State Key Laboratory for Mesoscopic Physics Frontiers Science Center for Nano-Optoelectronics&Collaborative Innovation Center of Quantum MatterSchool of PhysicsPeking UniversityBeijing 100871China College of Energy Xiamen UniversityXiamen 361102China

The properties of high entropy pyrochlore have been studied extensively,but there is no consistent conclusion on its radiation ***,the mechanism of the high entropy effect on the radiation tolerance of pyrochlore is still *** this work,combined with experiments and calculations of pyrochlores with similar cationic radius ratios,the A-site and B-site high entropy effects on structural evolution under irradiation are *** situ irradiation experiments were carried out on A-site high entropy pyrochlores such as(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Er_(0.2))_(2)Zr_(2)O_(7),B-site Gd_(2)(Ti_(1/3)Sn_(1/3)Zr_(1/3))_(2)O_(7),and ternary pyrochlore Sm_(2)Zr_(2)O_(7) and Gd_(2)Sn_(2)O_(7) for *** A-site high entropy pyrochlore can maintain a stable structure under high fluence irradiation like corresponding ternary pyrochlore,demonstrated by high angle annular dark field scanning transmission electron microscopy(HAADF-STEM),energy dispersive spectroscopy(EDS)mapping and Raman *** additional irradiation experiments on A-site high entropy pyrochlores(La_(1/3)Nd_(1/3)Gd_(1/3))_(2)Zr_(2)O_(7) and(Nd_(1/3)Sm_(1/3)Gd_(1/3))_(2)Zr_(2)O_(7) also confirm the similarity under irradiation between A-site high entropy and ternary ***,the B-site high entropy pyrochlore Gd_(2)(Ti_(1/3)Sn_(1/3)Zr_(1/3))_(2)O_(7) becomes amorphous at exceptionally low irradiation fluences,indicating a significantly distinct radiation tolerance compared with the A-site high *** difference between the A-site and B-site high entropy effect is analyzed from cationic lattice distortion,bond strength,and inner electron binding energy by first-principles *** results reveal the role and mechanism of the high entropy effect in pyrochlores and lay a foundation for material design and future applications.

关键词： High entropy pyrochlores In situ irradiation Crystal overlap Hamilton population Electron binding energy

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A Compact Eulerian Interface-Capturing Algorithm for Compressible Multimaterial Elastic-Plastic Flows with Mie-Gr uneisen Equation of State

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Advances in applied Mathematics and Mechanics 2023年第2期15卷 485-521页

作者： Xiang Li Dong-Jun Ma Nan-Sheng Liu Pei Wang Institute of Applied Physics and Computational Mathematics Beijing 100094China Department of Modern Mechanics University of Science and Technology of ChinaHefeiAnhui 230027China Center for Applied Physics and Technology Peking UniversityBeijing 100871China

This paper presents an Eulerian diffuse-interface method using a high-order compact difference scheme for simulating elastic-plastic flows with the Mie–Gruneisen(MG)equation of state(EoS).For simulations of multimaterial problems,numerical errors were generated in the material discontinuities owing to inconsistent treatment of the convective *** on the normal-stress-based mechanical equilibrium assumption for elastic-plastic solids,we introduce an improved form of the consistent localized artificial diffusivity(LAD)method to ensure an oscillation-free interface for velocity and normal *** proposed algorithm uses a hyperelastic model.A mixture type of the model system was formed by combining the conservation equations for the basic conserved variables,an equation of a unified deviatoric tensor describing solid deformation,and an additional set of equations for solving the material quantities in the MG *** one-and two-dimensional problems with various discontinuities,including the elastic-plastic Richtmyer–Meshkov instability,were considered for testing the proposed method.

关键词： Multimaterial elastic-plastic flow Eulerian solid-dynamics high-order accurate schemes compact finite difference localized artificial diffusivity

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