检索结果-南通市图书馆

A Modified Cellular Automaton Model for the Quantitative Prediction of Equiaxed and Columnar Dendritic Growth

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2014年第12期30卷 1311-1320页

作者： Rui Chen Qingyan Xu baicheng liu Key Laboratory for Advanced Materials Processing Technology School of Materials Science and Engineering Tsinghua University

Since the characteristic of dendrite is an important factor determining the performance of castings, a twodimensional cellular automaton model with decentered square algorithm is developed for quantitatively predicting the dendritic growth during solidification process. The growth kinetics of solid/liquid interface are determined by the local equilibrium composition and local actual liquid composition, and the calculation of the solid fraction increment is based on these two compositions to avoid the solution of growth velocity. In order to validate the developed model, quantitative simulations of steady-state dendritic features over a range of undercooling was performed and the results exhibited good agreement with the predictions of LGK（Liptone Glicksman-Kurz） model. Meanwhile, it is demonstrated that the proposed model can be applied to simulate multiple equiaxed dendritic growth, as well as columnar dendritic growth with or without equiaxed grain formation in directional solidification of AleC u alloys. It has been shown that the model is able to simulate the growth process of multi-dendrites with various preferential orientations and can reproduce a wide range of complex dendritic growth phenomena such as nucleation, coarsening of dendrite arms, side branching in dendritic morphologies, competitive growth as well as the interaction among surrounding dendrites.

关键词： Cellular automaton Dendritic growth Crystallographic orientation Aluminum alloys

Study on Dendritic Growth in Pressurized Solidification of Mg–Al Alloy Using Phase Field Simulation

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2016年第1期32卷 68-75页

作者： Haowei Pan Zhiqiang Han baicheng liu Key Laboratory for Advanced Materials Processing Technology Ministry of EducationSchool of Materials Science and EngineeringTsinghua University State Key Laboratory of Automotive Safety and Energy Department of Automotive EngineeringTsinghua University

A multi-grain phase field model coupled with thermodynamic calculation was adopted to describe the dendritic growth in pressurized solidification of Mg-A1 alloy during squeeze casting, in which the effects of the pressure on the Gibbs free energy and chemical potential of solid and liquid phases, the solute diffusion coefficient, and the solute partition coefficient were considered. The individual effect of solute diffusion coefficient, and the Gibbs free energy on the dendritic growth was studied. With the compar- ison of the dendritic growth under atmospheric and elevated pressures, the effect of pressure on the microstructure evolution was discussed. The results showed that the grains are refined, the dendritic growth rate tends to increase and the secondary dendrite arms are more developed as the pressure is increased from 0.1 to 100 MPa, which showed a good agreement with the experimental results of direct squeeze casting of Mg-AI alloy. As the pressure increases, the largest dendritic growth rate can be obtained under the pressure between 200 and 250 MPa, while the growth rate decreases with a further increase of pressure.

关键词： Phase field Pressurized solidification Dendritic growth Mg-Al alloy Gibbs free energy

3D Modeling and Simulation of Dendritic Growth during Solidification

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2003年第z1期19卷 1-4页

作者： Zuojian LIANG Qingyan XU baicheng liu Department of Mechanical Engineering Tsinghua University Beijing 100084 China Department of Mechanical Engineering Tsinghua University Beijing 100084 China Department of Mechanical Engineering Tsinghua University Beijing 100084 China

A mathematical model for the three-dimensional simulation of free dendritic growth and microstructure evolutionwas developed based on the growth mechanism of crystal grains and basic transfer equations such as heat, massand momentum transfer equations. Many factors including constitutional undercooling, curvature undercooling andanisotropy, which had vital influences on the microstructure evolution, were considered in the model. Simulated resultsshowed that final microstructural patterns and free dendritic growth could be predicted reasonably and calculatedresults were coincident with experimental The simulated results of free dendritic growth indicated that the strength ofanisotropy has significant effects on free dendritic growth, dendrite profile, micro solute and temperature *** dendritic grain profiles with fully-grown parallel secondary arm tend to be formed at the intensive anisotropy,while near octahedral grain profiles with small protuberances of surface at low strength of anisotropy. The simulatedresults of free dendritic growth also indicated that there are small molten pools left in interdendritic areas. This ishelpful to understand the fundamental of the formation of microstructure related defects such as microsegregationand microporosity.

关键词： Modeling and simulation, Dendritic grain growth, Microstructure evolution

Study on the effect of pressure on the equilibrium and stability of the solid-liquid interface in solidification of binary alloys

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2011年第2期54卷 479-483页

作者： HUANG XiaoRan HAN ZhiQiang liu baicheng Key Laboratory for Advanced Materials Processing Technology Ministry of Education Tsinghua University Beijing 100084 China State Key Laboratory of Automotive Safety and Energy Tsinghua University Beijing 100084 China

The equilibrium of the solid-liquid interface in pressurized solidification process of binary alloys was studied using the Gibbs theory, and the stability of the solid-liquid interface was discussed based on the consideration of the effects of pressure on the diffusion coefficient, the interface growth rate and tile equilibrium liquid composition. A mathematical description of the equi- librium status, the relationship of temperature, pressure, composition and interfacial tension was obtained, and further, a mathematical representation of the curvature radius of solid-liquid interface was developed, which facilitates a thorough understanding of the controlled variables of the interfacial stability.

关键词： pressurized solidification binary alloy interfacial equilibrium interfacial stability

A response to numerical benchmark for solidification of binary alloys: macro-segregation with thermo-solutal convection

在线全文

学校读者我要写书评

暂无评论

China Foundry 2012年第2期9卷 171-177页

作者： Li Wensheng Shen Houfa liu baicheng Key Laboratory for Advanced Materials Processing Technology Ministry of EducationDepartment of Mechanical EngineeringTsinghua University Beijing 100084China

As a necessary step toward the quantitative predictions of macro-segregation commonly found in metal castings, classical experiments and numerical benchmarks have been used to validate a simplified binary- alloy solidification model. The model consists of fully coupled conservation equations for the transport phenomena （heat transfer, solute redistribution, ~tnd melt convection） that lead to macro-segregation in a solidifying ingot with a fixed solid phase. Simulations were performed for solidification of either a Pb-48wt.%Sn or a Sn-5wt.%Pb alloy in a rectangular cavity. The present predictions were compared with experimental data and numerical reference results reported in the literature. Subsequently, the model was applied to a numerical benchmark problem described in the literature for solidification of a Sn-10wt.%Pb alloy. Simulation results for flow velocity, liquid fraction evolution, and macro-segregation maps also were compared with literature predictions, showing similar trends. It is concluded that additional comparisons to experimental results are still required to assess more complex solidification models.

关键词： benchmark solidification macro-segregation thermo-solutal convection

Cellular automaton simulation of peritectic solidification of a C-Mn steel

在线全文

学校读者我要写书评

暂无评论

China Foundry 2012年第3期9卷 221-225页

作者： Su Bin Han Zhiqiang liu baicheng Key Laboratory for Advanced Materials Processing Technology(Ministry of Education) Department of Mechanical EngineeringTsinghua University.Beijing 100084China

A cellular automaton model has been developed to simulate the microstructure evolution of a C-Mn steel during the peritectic solidification. In the model, the thermodynamics and solute diffusion of multi-component systems were taken into account by using Thermo-Calc and Dictra software package. Scheil model was used to predict the relationship between the solid fraction and the temperature, which was used to calculate the movement velocity of the L/δ and the L/y interfaces. A mixed-mode model in multi-component systems was adopted to calculate the movement velocity of the 6/7 interface. To validate the cellular automaton model, the variation of manganese distribution was studied. The simulated results showed a good agreement with experimental results reported in literatures. Meanwhile, the simulated growth kinetics of peritectic solidification agreed well with the experimental results obtained using confocal scanning laser microscopy （CSLM）. The model can simulate the growth kinetics of the peritectic solidification and the distribution of concentrations of all components in grains.

关键词： cellular automaton peritectic solidification C-Mn steel multi-component numerical simulation

Review of production status of heavysteel castings and key technologies for their manufacture in China

在线全文

学校读者我要写书评

暂无评论

China Foundry 2008年第1期5卷 1-6页

作者： Kang Jinwu Huang Tianyou liu baicheng Key Laboratory for Advanced Materials Processing Technology Ministry of Education R R. China Department of Mechanical Engineering Tsinghua University Beijing 100084 China

This paper expatiates on domestic status of heavy steel casting production, with a special focus on hydraulicturbine castings for Three Gorges Project. In China, there is magnificent demand for heavy castings with the rapidgrowth of the national economy in recent years and the expected high growth in the coming 10 to 20 years. Someheavy and large castings such as mill housing and hydraulic turbine runner crown, blade and band for Three GorgesProject have been successfully made. However, the domestic production capability is still far from meeting the giganticrequirements. The domestic capability still lags behind the world class level, and a lot of heavy castings still dependon import. The paper also gives a particular introduction of the key technologies in the manufacturing of heavy steelcastings like metal melting, foundry technology, heat treatment technology and numerical simulation technique, *** addition, several case studies on the application of numerical simulation in the production of heavy steel castingsare presented.

关键词： heavy steel casting numerical simulation foundry technology

Multiscale modelling and simulation of single crystal superalloy turbine blade casting during directional solidification process

在线全文

学校读者我要写书评

暂无评论

China Foundry 2014年第4期11卷 268-276页

作者： Xu Qingyan Zhang Hang liu baicheng School of Materials Science and Engineering Key Laboratory for Advanced Materials Processing TechnologyMinistry of EducationTsinghua University

As the key parts of an aero-engine,single crystal(SX)superalloy turbine blades have been the focus of much ***,casting defects often occur during the manufacturing process of the SX turbine *** and simulation technology can help to optimize the manufacturing process of SX *** coupled models were proposed and used to simulate the physical phenomena occurring during the directional solidification(DS)*** with heat transfer(macroscale)and grain growth(meso-scale),3D dendritic grain growth was calculated to show the competitive grain growth at *** grain selection behavior was studied by the simulation and *** results show that the geometrical structure and technical parameters had strong influences on the grain selection *** on the coupled models,heat transfer,grain growth and microstructure evolution of a complex hollow SX blade were *** the simulated and experimental results show that the stray grain occurred at the platform of the SX blade when a constant withdrawal rate was used in manufacturing *** order to avoid the formation of the stray crystal,the multi-scale coupled models and the withdrawal rate optimized technique were applied to the same SX turbine *** modeling results indicated that the optimized variable withdrawal rate can achieve SX blade castings with no stray grains,which was also proved by the experiments.

关键词： directional solidification single crystal superalloy turbine blade casting grain selection modeling and simulation

Multi-scale modeling of liquid-metal cooling directional solidification and solidification behavior of nickel-based superalloy casting

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第8期67卷 36-49页

作者： Xuewei Yan Qjngyan Xu Guoqiang Tian Quanwei liu Junxing Hou baicheng liu School of Aeronautical Engineering Zhengzhou University of AeronauticsZhengzhou 450046China School of Materials Science and Engineering Tsinghua UniversityKey Laboratory for Advanced Materials Processing TechnologyMinistry of EducationBeijing 100084China

Liquid-metal cooling(LMC)process can offer refinement of microstructure and reduce defects due to the increased cooling rate from enhanced heat extraction,and thus an understanding of solidification behavior in nickel-based superalloy casting during LMC process is essential for improving mechanical performance of single crystal(SC)*** this effort,an integrated heat transfer model coupling meso grain structure and micro dendrite is developed to predict the temperature distribution and microstructure evolution in LMC *** interpolation algorithm is used to deal with the macro-micro grids coupling *** algorithm of cells capture is also modified,and a deterministic cellular automaton(DCA)model is proposed to describe neighborhood cell *** addition,solute distribution is also considered to describe the dendrite *** measuring,EBSD,OM and SEM experiments are implemented to verify the proposed model,and the experiment results agree well with the simulation *** simulations are performed with a range of withdrawal rates,and the results indicate that 12 mm·min^(-1)is suitable for LMC process in this work,which can result in a fairly narrow and flat mushy zone and correspondingly exhibited fairly straight *** mushy zone length is about 4.8 mm in the steady state and the average deviation angle of grains is about 13.9°at the height 90 mm from the casting base under 12 mm·min^(-1)withdrawal *** competitive phenomenon of dendrites at different withdrawal rates is also observed,which has a great relevant to the temperature fluctuation.

关键词： Multi-scale model Numerical simulation Liquid-metal cooling Microstructure