Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size *** atoms that favorably segregate to grain boundaries pro...
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Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size *** atoms that favorably segregate to grain boundaries produce a pinning atmosphere that exerts a drag pressure on the boundary motion,which strongly affects the grain growth behavior during *** the current work,the characteristics of grain growth in an annealed Mg-1 wt.%Mn-1 wt.%Nd magnesium alloy were investigated by advanced experimental and modeling *** quasi in-situ orientation mappings with a scanning electron microscope were performed to track the evolution of local and global microstructural characteristics as a function of annealing *** segregation at targeted grain boundaries was measured using three-dimensional atom probe ***-set computer simulations were carried with different setups of driving forces to explore their contribution to the microstructure development with and without solute *** results showed that the favorable growth advantage for some grains leading to a transient stage of abnormal grain growth is controlled by several drivers with varying importance at different stages of *** longer annealing times,residual dislocation density gradients between large and smaller grains are no longer important,which leads to microstructure stability due to predominant solute *** fluctuations in residual dislocation energy and solute concentration near grain boundaries cause different boundary segments to migrate at different rates,which affects the average growth rate of large grains and their evolved shape.
In this paper, a three-dimensional numerical simulation of the merged droplet formation (MDF) in the double T-junction microchannel was performed to investigate the effects of the flow rate of the continuous phase, co...
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In this paper, a three-dimensional numerical simulation of the merged droplet formation (MDF) in the double T-junction microchannel was performed to investigate the effects of the flow rate of the continuous phase, continuous viscosity and the interfacial tension on the pressure by the level-set method. We divide the droplet formation process into three stages, namely filling, blocking and breakup. We define the time to generate a droplet as the droplet generation period. The characteristic length L/W (L is the length of the droplet, and W is the width of the main channel) decreases as the capillary number increases. The pressure (P-A) at a special position at the junction of the two phases occurs periodically during the droplet formation process, which directly and precisely reflects the mechanism of the MDF in the microchannel. Therefore, we define the time during the pressure fluctuates periodically as the pressure fluctuation period. New insights into the pressure during the MDF in the squeezing time are reported. The results show that the pressure fluctuation period and pressure drop period are the same as the droplet generation period. When the continuous flow rate and viscosity increase, the peak and valley values of P-A and the pressure drop increase, and the time of the pressure cycle decreases. However, when the interfacial tension increases, the peak and theperiod increase and the valley decreases. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
A conservative level-set method (LSM) embedded in a computational fluid dynamics (CFD) simulation provides a useful approach for the studying the physics and underlying mechanism in two-phase flow. Detailed two-dimens...
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A conservative level-set method (LSM) embedded in a computational fluid dynamics (CFD) simulation provides a useful approach for the studying the physics and underlying mechanism in two-phase flow. Detailed two-dimensional (2D) computational microfluidics flow simulations have been carried out to examine systematically the influence of different controlling parameters such as flow rates, viscosities, surface wettability, and interfacial tensions between two immiscible fluids on the non-Newtonian shear-thinning microdroplets generation process. For the two-phase flow system that neglects the Marangoni effect, the breakup process of shear-thinning microdroplets in cross-flowing immiscible liquids in a microfluidic device with a T-shaped geometry was predicted. Data for the rheological and physical properties of fluids obeying Carreau-Yasuda stress model were empirically obtained to support the computational work. The simulation results show that the relevant control parameters mentioned above have a strong impact on the size of shear-thinning droplets generated. Present computational studies on the role and relative importance of controlling parameters can be established as a conceptual framework of the non-Newtonian droplet generation process and relevant phenomena for future studies. (C) 2017 Elsevier Ltd. All rights reserved.
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