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.

Cellular Automaton Simulation of Microstructure Evolution for Friction Stir Blind Riveting

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Avik Samanta ◽  
Ninggang Shen ◽  
Haipeng Ji ◽  
Weiming Wang ◽  
Jingjing Li ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Cellular Automaton ◽  
Microstructure Evolution ◽  
Numerical Approach ◽  
Dislocation Dynamics ◽  
Grain Structure ◽  
Workpiece Material ◽  
Friction Stir ◽  
Ca Model

Friction stir blind riveting (FSBR) process offers the ability to create highly efficient joints for lightweight metal alloys. During the process, a distinctive gradient microstructure can be generated for the work material near the rivet hole surface due to high-gradient plastic deformation and friction. In this work, discontinuous dynamic recrystallization (dDRX) is found to be the major recrystallization mechanism of aluminum alloy 6111 undergoing FSBR. A cellular automaton (CA) model is developed for the first time to simulate the evolution of microstructure of workpiece material during the dynamic FSBR process by incorporating main microstructure evolution mechanisms, including dislocation dynamics during severe plastic deformation, dynamic recovery, dDRX, and subsequent grain growth. Complex thermomechanical loading conditions during FSBR are obtained using a mesh-free Lagrangian particle-based smooth particle hydrodynamics (SPH) method, and are applied in the CA model to predict the microstructure evolution near the rivet hole. The simulation results in grain structure agree well with the experiments, which indicates that the important characteristics of microstructure evolution during the FSBR process are well captured by the CA model. This study presents a novel numerical approach to model and simulate microstructure evolution undergoing severe plastic deformation processes.

Preparation of CoCrFeNiCuMnSix High Entropy Alloys and their Microstructure and Properties

2013 ◽  
Vol 750-752 ◽  
pp. 615-618 ◽  
Author(s):  
Li Sheng Zhang
Keyword(s):  
Phase Structure ◽  
Optical Microscope ◽  
Vacuum Arc ◽  
High Entropy Alloy ◽  
High Entropy Alloys ◽  
Dendrite Morphology ◽  
High Entropy ◽  
Bcc Structure ◽  
Si Content ◽  
Cast Microstructure

According to the design concept of multi-element high-entropy alloys, seven kinds of elements (Cr, Mn, Fe, Co, Ni, Cu and Si) were selected in this work to design a series of CoCrFeNiCuMnSix high entropy alloys. Metal power was melted by vacuum arc furnace. Cast microstructure and phase structure of the high entropy alloy were Characterized by optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD). And then, hardness, wear resistance and corrosion resistance were tested. Phase structure of cast microstructure, the morphology of the microstructure and mechanical properties of the CoCrFeNiCuMnSix high entropy alloys were researched systematic in the condition of different content Si. The results show that the crystal structure is simple BCC structure. With the increasing Si content, the alloy cast structure changes from dendrite morphology to cellular morphology. It was Si content that plays an important role in increasing significantly the hardness of the alloy. The hardness of the maximum value reaches to HV985.

FEM-Based Modeling of Dynamic Recrystallization of AISI 52100 Steel Using Cellular Automaton Method

2010 ◽  
Vol 447-448 ◽  
pp. 406-411 ◽  
Author(s):  
Ke Lu Wang ◽  
M.W. Fu ◽  
Jian Lu
Keyword(s):  
Dynamic Recrystallization ◽  
Cellular Automaton ◽  
True Strain ◽  
Testing Material ◽  
Strain And Strain Rate ◽  
Aisi 52100 ◽  
Aisi 52100 Steel ◽  
Simulation And Experiment ◽  
Ca Model ◽  
Kinetics Of

The dynamic recrystallization (DRX) behavior in the isothermal hot compression of AISI 52100 steel was analyzed by using the phenomenological-based cellular automaton (CA) algorithm. The developed CA model was coded into DEFORM platform, which is a Finite Element Method (FEM)-based software for simulation of material deformation process. The developed CA-model can thus predict the nucleation and growth kinetics of dynamically recrystallized grains of the testing material in hot working process. Furthermore, the effects of the deformation temperature, true strain and strain rate on the microstructural evolution of the testing material were physically studied by using Gleeble-1500 thermo-mechanical simulator and the developed CA-model was verified by the experimental results. Through simulation and experiment, it is found that the results predicted by the CA-model have a good agreement with the experimental ones.

Simulations of Microstructure Evolution During Friction Stir Blind Riveting Using a Cellular Automaton Method

2017 ◽  
Author(s):  
Avik Samanta ◽  
Ninggang Shen ◽  
Haipeng Ji ◽  
Weiming Wang ◽  
Hongtao Ding ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Cellular Automaton ◽  
Microstructure Evolution ◽  
Deformation Gradient ◽  
Microstructural Analysis ◽  
Numerical Approach ◽  
Friction Stir ◽  
Large Gradient ◽  
Gradient Microstructure ◽  
Ca Model

Friction stir blind riveting (FSBR) is a novel and highly efficient joining technique for lightweight metal materials, such as aluminum alloys. The FSBR process induced large gradients of plastic deformation near the rivet hole surface and resulted in a distinctive gradient microstructure in this domain. In this study, microstructural analysis is conducted to analyze the final microstructure after the FSBR process. Dynamic recrystallization (DRX) is determined as the dominant microstructure evolution mechanism due to the significant heat generation during the process. To better understand the FSBR process, a two-dimensional Cellular Automaton (CA) model is developed to simulate the microstructure evolution near the rivet hole surface by considering the FSBR process loading condition. To model the significant microstructure change near the rivet hole surface, spatial distributed temporal thermal and mechanical loading conditions are applied to simulate the effect of the large gradient plastic deformation near the hole surface. The distribution grain topography and recrystallization fraction are obtained through the simulations, which agree well with the experimental data. This study presents a reliable numerical approach to model and simulate microstructure evolution governed by DRX under the large plastic deformation gradient in FSBR.

Experimental Study and Numerical Simulation of Microstructure Evolution in Al-Si Eutectic Solidification Process

2018 ◽  
Vol 913 ◽  
pp. 212-219 ◽  
Author(s):  
Bing Wu ◽  
Ao Lei Jiang ◽  
Hao Lu ◽  
Hong Liang Zheng ◽  
Xue Lei Tian
Keyword(s):  
Numerical Simulation ◽  
Microstructure Evolution ◽  
Solidification Process ◽  
Eutectic Growth ◽  
Eutectic Structure ◽  
Solute Concentration ◽  
Optical Microscope ◽  
Eutectic Solidification ◽  
Eutectic Si ◽  
Ca Model

A mathematical physical model of microstructure evolution in Al-Si eutectic solidification process based on cellular automaton (CA) model was developed. Before the establishment of the model, the relevant near-eutectic experiments were carried out to analyze the effect of cooling rates measured by temperature curves on the eutectic structure which was observed through optical microscope (OM) and scanning electron microscope (SEM). Then a multiphase nucleation-growth CA model was applied to simulate the Al-Si irregular eutectic structure. The model adopted an alternative nucleation mechanism to investigate the influence of the critical nucleation value associated with solute concentration during solidification process. The growth kinetics took into account the solute and thermal field. According to the crystal structure of nonfaceted eutectic Al and faceted eutectic Si, different capturing rules were employed to calculate the growth of eutectic. In addition, the model was also used to research the irregular eutectic growth under different undercooling conditions. The results revealed that smaller critical nucleation value (absolute value) or higher eutectic undercooling tended to get a more refined eutectic microstructure. By compared with experimental results, it is indicated that the microstructure evolution of Al-Si eutectic growth can be reproduced quantitatively by numerical simulation with this model.

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.

Modeling of Microstructure Evolution in Nb-Si Eutectic Alloy Using Cellular Automaton Method

2008 ◽  
Vol 1128 ◽  
Author(s):  
Kenichi Ohsasa ◽  
Seiji Miura
Keyword(s):  
Cellular Automaton ◽  
Microstructure Evolution ◽  
Eutectic Alloy ◽  
Eutectic Composition ◽  
Eutectic Growth ◽  
Liquid Interface ◽  
Dendrite Morphology ◽  
Cellular Automaton Method ◽  
Solid Liquid Interface ◽  
Solid Liquid

AbstractA numerical model was developed for the simulation of microstructure evolution during the solidification of Nb-Si eutectic alloy. In this model, the cellular automaton method was used to simulate the eutectic growth of Nb solid solution and Nb3Si intermetallics. Diffusion in liquid, mass conservation at the solid/liquid interface and local equilibrium at the solid/liquid interface with consideration of curvature undercooling were solved to determine the positions of the Nb/liquid and Nb3Si/liquid interfaces. In the alloy with eutectic composition of 0.18at%Nb, irregular eutectic growth morphology was observed in relatively lower undercooling region. On the other hand, in higher undercooling region over 50K, dendrite morphology of Nb3Si was observed. An alloy with hypo-eutectic composition, cell and dendrite morphology were observed in lower undercooling region, while coupling eutectic morphology was formed in higher undercooling region over 25K.The growth velocity of the coupling growth increased with increase in the degree of undercooling of melt.

Kinetics of phase precipitation in Al-Mg-Si alloys subjected to equal-channel angular pressing during subsequent heating

2021 ◽  
pp. 160583
Author(s):  
N.R. Bochvar ◽  
O.V. Rybalchenko ◽  
N. Yu. Tabachkova ◽  
G.V. Rybalchenko ◽  
N.P. Leonova ◽  
...  
Keyword(s):  
Equal Channel Angular Pressing ◽  
Phase Precipitation ◽  
Angular Pressing ◽  
Subsequent Heating ◽  
Kinetics Of

Effect of Warm Deformation on Ferrite Microstructure Evolution in a Ti-Microalloyed Steel

2007 ◽  
Vol 558-559 ◽  
pp. 497-504
Author(s):  
Beitallah Eghbali
Keyword(s):  
Microstructure Evolution ◽  
Microalloyed Steel ◽  
Early Stage ◽  
Microstructural Analysis ◽  
Optical Microscope ◽  
Low Carbon ◽  
High Angle ◽  
Warm Deformation ◽  
Continuous Dynamic Recrystallization ◽  
Continuous Dynamic

Warm deformation is one of the promising hot rolling strategies for producing thin hot rolled steel strips. A better understanding of the microstructure evolution during warm deformation is important for a successful introduction of such processing into the industrial production. In the present research, the effect of deformation strain on the ferrite microstructure development in a low carbon Ti-microalloyed steel was investigated through warm torsion testing. Microstructural analysis with optical microscope and electron back-scattering diffraction was carried out on the warm deformed ferrite microstructures. The results show that at the early stage of deformation an unstable subboundaries network forms and low angle boundaries are introduced in the original grains. Then, with further straining, low angle boundaries transform into high angle boundaries and stable fine equiaxed ferrite grains form. It was considered that dynamic softening and dynamically formation of new fine ferrite grains, with high angle boundaries, were caused by continuous dynamic recrystallization of ferrite.

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