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Fabricating of Open-cell Porous Al-Si Alloy with Pressure Penetration Casting

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Journal of Materials Science & Technology 1999年第1期15卷 63-66页

作者： xu, qingyan Chen, Yuyong Li, Qingchun Harbin Inst Technol Met Casting Lab Harbin 150001 Peoples R China

Open-cell porous Al alloy was fabricated by pressure penetration method and the fabrication of preform was studied in detail. When forming temperature is about 700 degree C and binder content is about 10%, preform with high compressive strength was obtained. Good porous Al alloy with pore size 0.5-1.6 mm and porosity 60%-80% can be obtained under 100 degree C super-heating of liquid metal and about 1.0 MPa applied pressure. The size of the largest sample is up to 100 mm in diameter and 100 mm in height. With the help of SEM it was found that the obtained material is a three-dimensional open-cell porous structure with well-distributed and connected with each other pores. Finally, theoretical analysis was carried out to explain the effect of fabricating process. (Edited author abstract) 4 Refs.

关键词： Aluminum alloys

3D Modeling and Simulation of Dendritic Growth during Solidification

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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

Numerical Simulation of Solidification Process on Single Crystal Ni-Based Superalloy Investment Castings

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Journal of Materials Science & Technology 2007年第1期23卷 47-54页

作者： Jing YU qingyan xu Kai CUI Baicheng LIU Akihiko KIMATSUKA Key Laboratory for Advanced Materials Processing Technology Ministry of Education Department of Mechanical Engineering Tsinghua University Beijing 100084 China Ishikawajima-Harima Heavy Industries Co. Ltd. Isogo-Ku Yokohama 235-8501 Japan

Bridgman directional solidification of investment castings is a key technology for the production of reliable and highly efficient gas turbine blades. In this paper, a mathematical model for three-dimensional （3D） simulation of solidification process of single crystal investment castings was developed based on basic heat transfer equations. Complex heat radiation among the multiple blade castings and the furnace wall was considered in the model. Temperature distribution and temperature gradient in superalloy investment castings of single blade and multiple ones were investigated, respectively. The calculated cooling curves were compared with the experimental results and agreed well with the latter. It is indicated that the unsymmetrical temperature distribution and curved liquid-solid interface caused by the circle distribution of multiple turbine blades are probably main reasons why the stray grain and other casting defects occur in the turbine blade.

关键词： Directional solidification Single crystal Investment casting Numerical simulation

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

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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

Generation mechanism and motion behavior of sliver defect in single crystal Ni-based superalloy

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Journal of Materials Science & Technology 2023年第6期137卷 232-246页

作者： Huxiang Xia Yanhong Yang Qiushui Feng qingyan xu Hongbiao Dong Baicheng Liu Key Laboratory for Advanced Materials Processing Technology(MOE) School of Materials Science and EngineeringTsinghua UniversityBeijing100084China Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Engineering University of LeicesterLeicesterLE17RHUnited Kingdom

Sliver is a common but easily neglected defect in single crystal Ni-based superalloy *** date,there is still no unified viewpoint on its formation mechanism and generation *** this work,the orientation discontinuity and motion behavior of sliver defects were studied through experiments and numerical *** ultrathin wedge-shaped specimen containing the grain boundary of the sliver and the matrix was prepared at the initial position of the sliver defect for the observation of equal thick-ness *** discontinuity of equal thickness fringes on both sides of the grain boundary was ob-served through a transmission electron microscope,which directly confirms the abrupt change in the orientation between the sliver and matrix from the *** crystal lattices at the smooth area and the bulging area of the grain boundary were found to have unusually different *** irregular lattice arrangement at the bulging area shows that the grain boundary has experienced high-stress *** results of sliver orientation deviation with a further composition analysis show the micro protuberance of the mold shell has a noticeable inductive effect on the sliver ***,a self-developed three-dimensional phase-field simulation model coupled with the spatial topology algorithm is established to simulate the orientation deflection behavior and orientation devia-tion threshold of fractured *** simulation results indicated that there is an upper limit of the cross-section solid fraction at the fracture position for the motion of the fractured *** the cross-section solid fraction at the fracture position is higher than this upper limit,it will be difficult to produce large deviation slivers due to the structural limitation of surrounding *** upper limit does not change with the solidification temperature gradient.

关键词： Single crystal Ni-based superalloys Directional solidification Sliver defect Phase-field simulation

Numerical simulation for the investment casting process of a large-size titanium alloy thin-wall casing

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Progress in Natural Science:Materials International 2018年第4期28卷 520-528页

作者： Pan Tao Heng Shao Zhijun Ji Hai Nan qingyan xu Key Laboratory for Advanced Materials Processing Technology Ministry of Education School of Materials Science and Engineering Tsinghua University Beijing Institute of Aeronautical Materials

To optimize the investment casting process when producing high quality large-size titanium alloy thin-wall components is a time-consuming job due to the complicated metallurgical process. Numerical simulation is a high-efficiency method compared with trial and error, and therefore is introduced to the investment casting process optimization to shorten the new product development cycle and reduce the production cost. In this study, weakly compressible model(WCM) and ununiformed finite difference mesh(UFDM) was developed to reduce the memory consumption and ensure the simulation efficiency. The precision of the WCM and UFDM were verified by numerical simulation of cavity heat convection in a square cavity and hydraulics simulation of centrifugal filling in a transparent cavity. The numerical simulation of the investment casting process of a titanium alloy thin-wall casing under different process conditions was accomplished using a self-developed software, and the distribution characteristics of potential shrinkage defects were predicted. It was found that the predicted defects in the titanium alloy casing matched well with the actual X-ray experimental results. For the components investigated in this paper, more numerical simulation results show that the centrifugal casting process with respect to gravity casting had no obvious improvements in the concentrated shrinkage defects, and the gravity casting process can be more reasonable from the engineering point of view.

关键词： Titanium alloy Investment casting Numerical simulation Finite difference method Non-uniform mesh

Progress on modeling and simulation of directional solidification of superalloy turbine blade casting

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China Foundry 2012年第1期9卷 69-77页

作者： xu qingyan Liu Baicheng Pan Dong Yu Jing Key Laboratory for Advanced Materials Processing Technology MOEDepartment of Mechanical EngineeringTsinghua UniversityBeijing 100084China

Directional solidified turbine blades of Ni-based superalloy are widely used as key parts of the gas turbine *** mechanical properties of the blade are greatly influenced by the final microstructure and the grain orientation determined directly by the grain selector geometry of the *** this paper,mathematical models were proposed for three dimensional simulation of the grain growth and microstructure evolution in directional solidification of turbine blade ***-tracing method was applied to calculate the temperature variation of the *** on the thermo model of heat transfer,the competitive grain growth within the starter block and the spiral of the grain selector,the grain growth in the blade and the microstructure evolution were simulated via a modified Cellular Automaton *** experiments were carried out,and the measured results were compared quantitatively with the predicted *** simulated cooling curves and microstructures corresponded well with the experimental *** proposed models could be used to predict the grain morphology and the competitive grain evolution during directional solidification.

关键词： Ni-based superalloy microstructure directional solidification modeling

Numerical simulation of microstructure evolution during directional solidification process in directional solidified (DS) turbine blades

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Science China(Technological Sciences) 2011年第12期54卷 3191-3202页

作者： ZHANG Hang xu qingyan TANG Ning PAN Dong LIU BaiCheng Key Laboratory for Advanced Materials Processing Technology Ministry of Education Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Directional solidified(DS) turbine blades are widely used in advanced gas turbine engine. The size and orientation of columnar grains have great influence on the high temperature property and performance of the turbine blade. Numerical simulation of the directional solidification process is an effective way to investigate the grain's growth and morphology,and hence to optimize the process. In this paper,a mathematical model was presented to study the directional solidified microstructures at different withdrawal rates. Ray-tracing method was applied to calculate the temperature variation of the blade. By using a Modified Cellular Automation(MCA) method and a simple linear interpolation method,the mushy zone and the microstructure evolution were studied in detail. Experimental validations were carried out at different withdrawal rates. The calculated cooling curves and microstructure agreed well with those experimental. It is indicated that the withdrawal rate affects the temperature distribution and growth rate of the grain directly,which determines the final size and morphology of the columnar grain. A moderate withdrawal rate can lead to high quality DS turbine blades for industrial application.

关键词： directional solidified (DS) turbine blade Cellular Automation (CA) numerical modeling and simulation

Three-dimensional microstructure simulation of Ni-based superalloy investment castings

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Science China(Physics,Mechanics & Astronomy) 2011年第5期54卷 851-855页

作者： PAN Dong xu qingyan LIU BaiCheng Key Laboratory for Advanced Materials Processing Technology Ministry of Education Department of Mechanical Engineering Tsinghua University Beijing 100084 China

An integrated macro and micro multi-scale model for the three-dimensional microstructure simulation of Ni-based superalloy investment castings was developed, and applied to industrial castings to investigate grain evolution during solidification. A ray tracing method was used to deal with the complex heat radiation transfer. The rnicrostructure evolution was simulated based on the Modified Cellular Automaton method, which was coupled with three-dimensional nested macro and micro grids. Experi- ments for Ni-based superalloy turbine wheel investment casting were carried out, which showed a good correspondence with the simulated results. It is indicated that the proposed model is able to predict the microstructure of the casting precisely, which provides a tool for the optimizing process.

关键词： microstructure simulation Ni-based superalloy investment casting