scholarly journals CA Modeling of Microsegregation and Growth of Equiaxed Dendrites in the Binary Al-Mg Alloy

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3393
Author(s):  
Andrzej Zyska
Keyword(s):  
Cellular Automaton ◽  
Cross Section ◽  
Solid Phase ◽  
Mg Alloy ◽  
Magnesium Concentration ◽  
Dendrite Morphology ◽  
Initial Stage ◽  
Phase Transition Temperatures ◽  
Transformation Time ◽  
Ca Model

A two-dimensional model based on the Cellular Automaton (CA) technique for simulating free dendritic growth in the binary Al + 5 wt.% alloy was presented. In the model, the local increment of the solid fraction was calculated using a methodology that takes into account changes in the concentration of the liquid and solid phase component in the interface cells during the solidification transition. The procedure of discarding the alloy component to the cells in the immediate vicinity was used to describe the initial, unstable dendrite growth phase under transient diffusion conditions. Numerical simulations of solidification were performed for a single dendrite using cooling rates of 5, 25 and 45 K/s and for many crystals assuming the boundary condition of the third kind (Newton). The formation and growth of primary and secondary branches as well as the development of component microsegregation in the liquid and solid phase during solidification of the investigated alloy were analysed. It was found that with an increase in the cooling rate, the dendrite morphology changes, its cross-section and the distance between the secondary arms decrease, while the degree of component microsegregation and temperature recalescence in the initial stage of solidification increase. In order to determine the potential of the numerical model, the simulation results were compared with the predictions of the Lipton–Glicksman–Kurz (LGK) analytical model and the experimental solidification tests. It was demonstrated that the variability of the dendrite tip diameter and the growth rate determined in the Cellular Automaton (CA) model are similar to the values obtained in the LGK model. As part of the solidification tests carried out using the Derivative Differential Thermal Analysis (DDTA) method, a good fit of the CA model was established in terms of the shape of the solidification curves as well as the location of the characteristic phase transition temperatures and transformation time. Comparative tests of the real structure of the Al + 5 wt.% Mg alloy with the simulated structure were also carried out, and the compliance of the Secondary Dendrite Arm Spacing (SDAS) parameter and magnesium concentration profiles on the cross-section of the secondary dendrites arms was assessed.

scholarly journals Cellular Automaton Modeling of Phase Transformation of U-Nb Alloys during Solidification and Consequent Cooling Process

2019 ◽  
Vol 38 (2019) ◽  
pp. 567-575 ◽  
Author(s):  
Qingfu Tang ◽  
Dong Chen ◽  
Bin Su ◽  
Xiaopeng Zhang ◽  
Hongzhang Deng ◽  
...  
Keyword(s):  
Cellular Automaton ◽  
Microstructure Evolution ◽  
Optical Microscope ◽  
Phase Precipitation ◽  
Cooling Process ◽  
Dendrite Morphology ◽  
Ca Model ◽  
Measuring Experiment ◽  
Kinetics Of ◽  
Cast Microstructure

AbstractThe microstructure evolution of U-Nb alloys during solidification and consequent cooling process was simulated using a cellular automaton (CA) model. By using this model, ϒ phase precipitation and monotectoid decomposition were simulated, and dendrite morphology of ϒ phase, Nb microsegregation and kinetics of monotectoid decomposition were obtained. To validate the model, an ingot of U-5.5Nb (wt.%) was produced and temperature measuring experiment was carried out. As-cast microstructure at different position taken from the ingot was investigated by using optical microscope and SEM. The effect of cooling rate on ϒ phase precipitation and monotectoid decomposition of U-Nb alloys was also studied. The simulated results were compared with the experimental results and the capability of the model for quantitatively predicting the microstructure evolution of U-Nb alloys during solidification and consequent cooling process was assessed.

scholarly journals Investigation into microstructure and element segregation of Inconel 713LC during SLM processing using modified cellular automaton model

2021 ◽  
Author(s):  
Amir Ansari Dezfoli ◽  
Yu-Lung Lo ◽  
M. Mohsin Raza
Keyword(s):  
Experimental Investigation ◽  
Energy Density ◽  
Cellular Automaton ◽  
Solid Phase ◽  
Laser Energy ◽  
Crack Density ◽  
Laser Energy Density ◽  
Ca Model ◽  
Solidification Speed ◽  
Element Segregation

Abstract A numerical and experimental investigation is performed into the feasibility of fabricating IN713LC components using selective laser melting (SLM) through an appropriate control of the solidification speed, microstructure formation and element segregation. A modified Cellular Automaton (CA) model is developed to explore the nucleation, grain growth and element segregation behavior of IN713LC during ultra-fast solidification. It is found that the undesired phase formation which occurs during SLM processing of IN713LC is caused by the micro segregation of Nb, Ti, Mo and C at the grain boundaries. It is further shown that the micro segregation intensity depends on the solidification speed, which is determined in turn by the laser energy density. In particular, a lower laser energy density increases the solidification speed and results in a more uniform solid phase, thereby reducing the risk of crack formation. The simulation results are verified by experimental investigation. The results confirm that a lower laser energy density reduces the crack density and crack length. Finally, a crack-free IN713LC SLM sample is successfully produced by reducing the energy density from 360 to 170 J/m.

scholarly journals Polymer Binders of Ceramic Nanoparticles for Precision Casting of Nickel-Based Superalloys

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1714
Author(s):  
Paweł Wiśniewski
Keyword(s):  
Solid Phase ◽  
Average Particle Size ◽  
Water Soluble ◽  
Ethyl Silicate ◽  
Average Particle ◽  
Precision Casting ◽  
Polymer Binders ◽  
Initial Stage ◽  
Nano Alumina ◽  
Solid Phase Content

This study presents the general characteristics of binders used in precision casting of Nickel-based superalloys. Three groups of binders were described: resins, organic compounds, and materials containing nanoparticles in alcohol or aqueous systems. This study also includes literature reports on materials commonly used and those recently replaced by water-soluble binders, i.e., ethyl silicate (ES) and hydrolysed ethyl silicate (HES). The appearance of new and interesting solutions containing nano-alumina is described, as well as other solutions at the initial stage of scientific research, such as those containing biopolymers, biodegradable polycaprolactone (PCL), or modified starch. Special attention is paid to four binders containing nano-SiO2 intended for the first layers (Ludox AM, Ludox SK) and structural layers (EHT, Remasol) of shell moulds. Their morphology, viscosity, density, reactions, and electrokinetic potential were investigated. The binders were characterized by a high solid-phase content (>28%), viscosity, and density close to that of water (1–2 mPa·s) and good electrokinetic stability. The nanoparticles contained in the binders were approximately spherically shaped with an average particle size of 16–25 nm.

Binary Mixture of Solid-Solid Phase Change Material: Synthesis, Characterization and Experimental Study

2020 ◽  
Vol 978 ◽  
pp. 407-420
Author(s):  
Cyril Reuben Raj ◽  
S. Suresh ◽  
Arijit Upadhyay ◽  
K. Akash Govind ◽  
R. Nivethaa
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Solid Phase ◽  
Electronic System ◽  
Laser Flash ◽  
Phase Identification ◽  
Heating And Cooling ◽  
Blending Method ◽  
Phase Transition Temperatures ◽  
Change Material

In this work, a class of polyol solid-solid phase change material where Neopentyl glycol is mixed in 6 and 2 wt.% of Pentaerythritol and was synthesized by physical blending method to obtain homogeneous mixture and thermally cycled for 500 times. The surface morphology, chemical composition, crystal phase identification, thermal degradation, and phase change phenomena were characterized. The phase transition temperatures and enthalpies upon heating and cooling of 6 and 2 wt.% of Pentaerythritol are found to be 43.1 °C, 133 J g-1, and 28.2 °C, 119 J g-1, and 41.2 °C, 121 J g-1, and 28.5 °C, 106 J g-1, respectively which suits for electronic system to keep under operating zone. Laser Flash Apparatus was used to find the thermal diffusivity and thermal conductivity value was calculated. Further, the effect of heat transfer in binary polyol mixtures were experimentally analysed through conventional heat sink for electronic cooling application.

Interaction of Components of Co-Sn and Co-Sn-Cu Powder Materials in Liquid Phase Sintering

2019 ◽  
Vol 943 ◽  
pp. 113-118
Author(s):  
Evgeniy Georgiyevich Sokolov ◽  
Alexander Vitalyevich Ozolin ◽  
Lev Ivanovich Svistun ◽  
Svetlana Alexandrovna Arefieva
Keyword(s):  
Liquid Phase ◽  
Solid Phase ◽  
Steel Substrate ◽  
Liquid Phase Sintering ◽  
Powder Materials ◽  
Cu Alloys ◽  
Initial Stage ◽  
Interaction Of Components ◽  
Sintered Alloys ◽  
Liquid Tin

The interaction of components and structure formation were studied in liquid phase sintering of Co-Sn and Co-Sn-Cu powder materials. The powders of commercially pure metals were mixed with an organic binder and applied on the steel substrate. Sintering was performed under vacuum at temperatures of 820 and 1100 °C. The structure of sintered alloys was investigated by X-ray diffractometry and electron probe microanalysis, and microhardness (HV0.01) of the structural components was measured. It has been found that the nature of interaction of the liquid tin with the solid phase at the initial stage of sintering affects the formation of structure and porosity of Co-Sn and Co-Sn-Cu alloys considerably. In Co-Sn alloys, diffusion of tin into cobalt particles leads to the formation of intermetallic compounds, which hinders spreading of the liquid phase. This results in a porous defect structure formed in Co-Sn alloys. In Co-Sn-Cu alloys, at the initial stage of sintering the liquid phase enriched with copper is formed that wets the cobalt particles and contributes to their regrouping. As a result of this, materials with minor porosity are formed.

Modeling and Simulation of Microstructure Evolution of Cast Mg Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 1562-1568 ◽  
Author(s):  
Liang Huo ◽  
Zhi Qiang Han ◽  
Bai Cheng Liu
Keyword(s):  
Solute Transport ◽  
Magnesium Alloys ◽  
Microstructure Evolution ◽  
Local Equilibrium ◽  
Equilibrium Composition ◽  
Mg Alloy ◽  
Dendrite Morphology ◽  
Dendrites Growth ◽  
The Difference ◽  
Cast Magnesium

A cellular automaton (CA) model has been developed for simulating the microstructure evolution and dendrite morphology of cast magnesium alloys. The growth kinetics of dendrite tips is determined by the difference between local equilibrium composition and local actual composition obtained by solving the solute transport equation. Two sets of meshes, a hexagonal mesh and an orthogonal mesh, are used in the model to perform the simulation. The hexagonal mesh is used to perform CA calculation to reflect the texture of Mg alloy dendrites, and the orthogonal mesh is used to solve the solute transport equations. The model was applied to simulate single dendrite evolution and columnar dendrites growth of AZ91D Mg alloy, as well as multi-grain growth of Mg-10Gd-2Y-0.5Zr (wt%) Mg alloy. Permanent mold step-shaped castings of the two Mg alloys were poured and metallographic examinations were carried out for validating the present model. The simulation results agree well with metallographic results. The model can be applied to simulate the microstructure evolution and dendrite morphology of magnesium alloys.

A Cellular Automaton Model and its Application on Emotional Infections

2014 ◽  
Author(s):  
Zhao Liu ◽  
Huan Zhang ◽  
Taide Tan ◽  
Changxiong Qin ◽  
Jing Fan
Keyword(s):  
Theoretical Analysis ◽  
Organizational Behavior ◽  
Cellular Automaton ◽  
Positive Emotion ◽  
Positive Emotions ◽  
Emotional Contagion ◽  
Cellular Automaton Model ◽  
Reaction Process ◽  
Probabilistic Theory ◽  
Ca Model

Emotional contagion has been a focus problem in the current fields of psychology and organizational behavior. Based on the theoretical analysis of the emotional contagion mechanisms and probabilistic theory, a cellular automaton (CA) model has been proposed to simulate the process of emotional contagion. And with the help of this CA model, we study the gross features of employees’ positive emotions in the evolution of emotional contagion and explore the effects of employees’ ability to transport emotion susceptibility and intimacy on the reaction process. The results indicate that employees’ ability to transport positive emotion susceptibility and intimacy are positive related to the emotional contagion between employees.

A cellular automaton simulation of W–Ni alloy solidification in laser solid forming process

2017 ◽  
Vol 02 (04) ◽  
pp. 1750016
Author(s):  
Haiou Yang ◽  
Lei Wei ◽  
Xin Lin
Keyword(s):  
Cellular Automaton ◽  
Laser Remelting ◽  
Dimensional Model ◽  
Forming Process ◽  
Microstructure Simulation ◽  
Melt Pool ◽  
Laser Solid Forming ◽  
Ni Alloy ◽  
Ca Model ◽  
Metallurgy Process

An alloy cellular automaton (CA) model is developed for the microstructure simulation in directional solidification and laser solid forming (LSF) process. The CA model's capture rule was modified by a limited neighbor solid fraction (LNSF) method. A multiscale two-dimensional model is presented for simulating laser remelting process, which is the same as LSF without the addition of metallic powders into melt pool. The metallurgy process in melt pool was simulated, including temperature distribution, pool shape and solidification of microstructure. The microstructure evolution of tungsten–nickel alloy (W–Ni) during LSF is also simulated by present CA model.

Investigation of Homogenization Process of the 5019 Alloy Extrusion Billets

2016 ◽  
Vol 682 ◽  
pp. 10-17 ◽  
Author(s):  
Antoni Woźnicki ◽  
Dariusz Leśniak ◽  
Grzegorz Włoch ◽  
Alicja Wojtyna ◽  
Monika Zabrzańska
Keyword(s):  
Cross Section ◽  
Cast Alloy ◽  
Solidus Temperature ◽  
Magnesium Concentration ◽  
Cast State ◽  
Dendritic Microstructure ◽  
Cast Material ◽  
Soaking Time ◽  
Prolonged Annealing ◽  
Microstructural Effects

In the paper, the influence of homogenization parameters on the microstructure and properties of the 5019 alloy DC-cast billets was analysed. At the first stage, the microstructure of the alloy in as-cast state was investigated using SEM/EDS technique. Additionally, a DSC test and hardness measurements were performed. In the as-cast material, the presence of the dendritic microstructure with a pronounced microsegregation of magnesium in the dendrites cross-section was found. Subsequently, the specimens were subjected to laboratory homogenization experiments, with different soaking conditions and water quenching. The microstructural effects of the investigated variants of homogenization were evaluated using the same techniques as in the case of the as-cast alloy. It was found that after homogenization, with soaking at the temperature of 530 °C for 6 hours, the microsegregation is eliminated and the concentration of magnesium in the grains centres is over two times greater than in the dendrites cores before annealing. The solidus temperature rises by about 12 °C in comparison to the as-cast state. Neither extending the soaking time nor rising the temperature contributes to a further increase of the solidus temperature, or the magnesium concentration in the grains interiors. However, the tendency of dispersoids to grow and the change of Fe-bearing constituents chemical composition were observed after the high temperature, or prolonged annealing variants.

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