The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform
Peng Peng - One of the best experts on this subject based on the ideXlab platform.
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Determination of the liquid diffusion coefficient of the Sn-Ni peritectic alloy through temperature gradient zone melting
International Journal of Heat and Mass Transfer, 2020Co-Authors: Peng Peng, Jinmian Yue, Anqiao ZhangAbstract:Abstract In the present work, a new method determining the liquid phase diffusion coefficients DL in a binary peritectic alloy is presented. This method is based on the evolution in both the microstructure and melt concentrations which can be linked through liquid droplet migration in the Mushy zone during thermal stabilization. The thermal stabilization experiments of different time (2 to 8 h) are performed on Sn–Ni peritectic alloy (L+Ni3Sn2→Ni3Sn4) in a Bridgman-type directional solidification furnace. Two different Mushy Zones are formed during thermal stabilization of samples which are kept still in the furnace. The diffusion-controlled liquid droplet migration is caused by remelting/resolidification by temperature gradient zone melting (TGZM). It leads to not only the variation of volume fractions of solid(fS)/liquid(fL) phases in the Mushy zone but also the increase of the melt concentration in the complete-liquid zone C. Thus, based on the conservation of mass during thermal stabilization, fS and fL can be correlated to not only the liquid droplet migration velocity vm but also the melt concentration in the complete-liquid zone C during thermal stabilization. Since fS and fL can be easily obtained through microstructure analysis, the experimental value of vm at specific location/temperature is given. Then, the expression of vm which is function of DL is provided by an analytical model describing the remelting/resolidification process during the liquid migration. Finally, DL and the activation energy of the Sn-Ni peritectic alloy are obtained by equating the experimental values of vm with the expression of vm by this analytical model.
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Morphology evolution of the interface between different Mushy Zones of a Sn-Ni peritectic alloy in a temperature gradient
Materials Letters, 2016Co-Authors: Peng PengAbstract:Abstract During thermal stabilization, the (Ni 3 Sn 2 +liquid) and (Ni 3 Sn 4 +liquid) Mushy Zones were formed between the complete liquid zone and the non-molten zone due to the imposed temperature gradient. The morphology of the interface between these Mushy Zones changed during thermal stabilization. A thin liquid film which gradually disappeared was formed between the Mushy Zones at the initial of thermal stabilization. Due to the solute diffusion through the liquid channels by temperature gradient zone melting (TGZM), the triple junctions at T P gradually moved upwards, leading to serrated interface. If the thermal stabilization time is long enough, this interface is smoothed.
Mingfang Zhu - One of the best experts on this subject based on the ideXlab platform.
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Modeling of dendrite arm fragmentation and dendrite arm coarsening
'Springer Science and Business Media LLC', 2020Co-Authors: Hui Fang, Qingyu Zhang, Hua Xue, Shiyan Pan, Mingfang ZhuAbstract:A two-dimensional quantitative cellular automaton (CA) model is employed to simulate dendrite arm fragmentation and dendrite arm coarsening in Mushy Zones. The phenomenon of dendrite arm fragmentation of an Al-Cu alloy during heating is well represented by the CA simulation, and it is analyzed in detail by comparing the local actual concentration and local equilibrium concentration. The CA simulations for the dendritic microstructures of SCN-ACE alloys during isothermal holding in a Mushy zone reproduce the typical dendrite coarsening features as observed in experiments. The effects of holding temperature and alloy composition on the microstructures and dendrite coarsening kinetics are investigated. It is found that the melting of small dendrite arms and interdendritic groove advancement are the two main mechanisms in dendrite coarsening. The mechanism of coalescence by joining arm tips is more likely to take place at a lower temperature or for a lower alloy composition, while the dendrite arm fragmentation mechanism tends to occur at a higher temperature. The coarsening rate constant is found to decrease with increasing holding temperature and alloy composition
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Microstructural evolution during temperature gradient zone melting: Cellular automaton simulation and experiment
Computational Materials Science, 2018Co-Authors: Qingyu Zhang, Hua Xue, Qianyu Tang, Shiyan Pan, Markus Rettenmayr, Mingfang ZhuAbstract:Abstract The microstructural evolution in Mushy Zones of alloys due to temperature gradient zone melting (TGZM) is studied by simulations using a two-dimensional quantitative cellular automaton (CA) model and in situ observations of directional solidification with a transparent organic SCN-ACE alloy. The present model is an extension of a previous CA model by involving the mechanisms of both solidification and melting. The present CA model is adopted to simulate the temporal evolution of the position and velocity of a liquid pool migrating in the solid matrix of a SCN–0.3 wt% ACE alloy under conditions that the pulling velocity is either lower or higher than the critical pulling velocity. The CA simulated position and velocity curves agree well with analytical solutions. Simulations are also performed for the microstructural evolution of columnar dendrites in a SCN–2.0 wt% ACE alloy held in a stationary temperature gradient using the present CA model and a previous CA model that does not include the melting mechanism under otherwise identical conditions for comparison. The results show how melting is essential to dendrite arm migration in a temperature gradient. The time-averaged velocities of arm migration obtained from the present CA simulations increase with increasing temperature gradient and with decreasing the length between the initial arm position and the liquidus. This agrees reasonably well with experimental measurements and analytical predictions. The mechanisms of dendrite arm migration are investigated in detail by comparing the local equilibrium and actual liquid compositions at solid/liquid interfaces. The simulations render visualizing the complex interactions among local temperature, solute distribution/diffusion, and solidification/melting during the TGZM process.
Qingyu Zhang - One of the best experts on this subject based on the ideXlab platform.
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Modeling of dendrite arm fragmentation and dendrite arm coarsening
'Springer Science and Business Media LLC', 2020Co-Authors: Hui Fang, Qingyu Zhang, Hua Xue, Shiyan Pan, Mingfang ZhuAbstract:A two-dimensional quantitative cellular automaton (CA) model is employed to simulate dendrite arm fragmentation and dendrite arm coarsening in Mushy Zones. The phenomenon of dendrite arm fragmentation of an Al-Cu alloy during heating is well represented by the CA simulation, and it is analyzed in detail by comparing the local actual concentration and local equilibrium concentration. The CA simulations for the dendritic microstructures of SCN-ACE alloys during isothermal holding in a Mushy zone reproduce the typical dendrite coarsening features as observed in experiments. The effects of holding temperature and alloy composition on the microstructures and dendrite coarsening kinetics are investigated. It is found that the melting of small dendrite arms and interdendritic groove advancement are the two main mechanisms in dendrite coarsening. The mechanism of coalescence by joining arm tips is more likely to take place at a lower temperature or for a lower alloy composition, while the dendrite arm fragmentation mechanism tends to occur at a higher temperature. The coarsening rate constant is found to decrease with increasing holding temperature and alloy composition
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Microstructural evolution during temperature gradient zone melting: Cellular automaton simulation and experiment
Computational Materials Science, 2018Co-Authors: Qingyu Zhang, Hua Xue, Qianyu Tang, Shiyan Pan, Markus Rettenmayr, Mingfang ZhuAbstract:Abstract The microstructural evolution in Mushy Zones of alloys due to temperature gradient zone melting (TGZM) is studied by simulations using a two-dimensional quantitative cellular automaton (CA) model and in situ observations of directional solidification with a transparent organic SCN-ACE alloy. The present model is an extension of a previous CA model by involving the mechanisms of both solidification and melting. The present CA model is adopted to simulate the temporal evolution of the position and velocity of a liquid pool migrating in the solid matrix of a SCN–0.3 wt% ACE alloy under conditions that the pulling velocity is either lower or higher than the critical pulling velocity. The CA simulated position and velocity curves agree well with analytical solutions. Simulations are also performed for the microstructural evolution of columnar dendrites in a SCN–2.0 wt% ACE alloy held in a stationary temperature gradient using the present CA model and a previous CA model that does not include the melting mechanism under otherwise identical conditions for comparison. The results show how melting is essential to dendrite arm migration in a temperature gradient. The time-averaged velocities of arm migration obtained from the present CA simulations increase with increasing temperature gradient and with decreasing the length between the initial arm position and the liquidus. This agrees reasonably well with experimental measurements and analytical predictions. The mechanisms of dendrite arm migration are investigated in detail by comparing the local equilibrium and actual liquid compositions at solid/liquid interfaces. The simulations render visualizing the complex interactions among local temperature, solute distribution/diffusion, and solidification/melting during the TGZM process.
Markus Apel - One of the best experts on this subject based on the ideXlab platform.
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Evolution of a Mushy zone in a static temperature gradient using a volume average approach
Acta Materialia, 2017Co-Authors: Andre Phillion, G. Reinhart, H. Nguyen Thi, G. Salloum-abou-jaoude, Miha Založnik, I. Spindler, N. Pinter, C.-a. Aledo, Guillaume Boussinot, Markus ApelAbstract:A volume average model to study the transition of a semi-solid Mushy zone to a planar solid/liquid interface in a static temperature gradient is presented. This model simulates the principal phenomena governing Mushy zone dynamics including solute diffusion in the interdendritic and bulk liquids, migration of both the solid-liquid interface and the Mushy-liquid boundary at the bottom and top of the Mushy zone, and solidification. The motion of the solid-liquid interface is determined analytically by performing a microscopic solute balance between the solid and Mushy Zones. The motion of the Mushy-liquid boundary is more complex as it consists of a transition between the Mushy and bulk liquid Zones with rapidly changing macroscopic properties. In order to simulate this motion, a control volume characterized by continuity in the solute concentration and a jump in both the liquid fraction and the solute concentration gradient was developed. The volume average model has been validated by comparison against prior in-situ X-ray radiography measurements [1], and phase-field simulations [2] of the Mushy-to-planar transition in an Al-Cu alloy. A very good similarity was achieved between the observed experimental and phase-field dynamics with this new model even though the described system was only one-dimensional. However , an augmentation of the solute diffusion coefficient in the bulk liquid was required in order to mimic the convective solute transport occurring in the in situ X-ray study. This new model will be useful for simulating a wide range of natural and engineering processes.
Shiyan Pan - One of the best experts on this subject based on the ideXlab platform.
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Modeling of dendrite arm fragmentation and dendrite arm coarsening
'Springer Science and Business Media LLC', 2020Co-Authors: Hui Fang, Qingyu Zhang, Hua Xue, Shiyan Pan, Mingfang ZhuAbstract:A two-dimensional quantitative cellular automaton (CA) model is employed to simulate dendrite arm fragmentation and dendrite arm coarsening in Mushy Zones. The phenomenon of dendrite arm fragmentation of an Al-Cu alloy during heating is well represented by the CA simulation, and it is analyzed in detail by comparing the local actual concentration and local equilibrium concentration. The CA simulations for the dendritic microstructures of SCN-ACE alloys during isothermal holding in a Mushy zone reproduce the typical dendrite coarsening features as observed in experiments. The effects of holding temperature and alloy composition on the microstructures and dendrite coarsening kinetics are investigated. It is found that the melting of small dendrite arms and interdendritic groove advancement are the two main mechanisms in dendrite coarsening. The mechanism of coalescence by joining arm tips is more likely to take place at a lower temperature or for a lower alloy composition, while the dendrite arm fragmentation mechanism tends to occur at a higher temperature. The coarsening rate constant is found to decrease with increasing holding temperature and alloy composition
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Microstructural evolution during temperature gradient zone melting: Cellular automaton simulation and experiment
Computational Materials Science, 2018Co-Authors: Qingyu Zhang, Hua Xue, Qianyu Tang, Shiyan Pan, Markus Rettenmayr, Mingfang ZhuAbstract:Abstract The microstructural evolution in Mushy Zones of alloys due to temperature gradient zone melting (TGZM) is studied by simulations using a two-dimensional quantitative cellular automaton (CA) model and in situ observations of directional solidification with a transparent organic SCN-ACE alloy. The present model is an extension of a previous CA model by involving the mechanisms of both solidification and melting. The present CA model is adopted to simulate the temporal evolution of the position and velocity of a liquid pool migrating in the solid matrix of a SCN–0.3 wt% ACE alloy under conditions that the pulling velocity is either lower or higher than the critical pulling velocity. The CA simulated position and velocity curves agree well with analytical solutions. Simulations are also performed for the microstructural evolution of columnar dendrites in a SCN–2.0 wt% ACE alloy held in a stationary temperature gradient using the present CA model and a previous CA model that does not include the melting mechanism under otherwise identical conditions for comparison. The results show how melting is essential to dendrite arm migration in a temperature gradient. The time-averaged velocities of arm migration obtained from the present CA simulations increase with increasing temperature gradient and with decreasing the length between the initial arm position and the liquidus. This agrees reasonably well with experimental measurements and analytical predictions. The mechanisms of dendrite arm migration are investigated in detail by comparing the local equilibrium and actual liquid compositions at solid/liquid interfaces. The simulations render visualizing the complex interactions among local temperature, solute distribution/diffusion, and solidification/melting during the TGZM process.
