scholarly journals Atomic-Scale Mechanism Investigation of Mass Transfer in Laser Fabrication Process of Ti-Al Alloy via Molecular Dynamics Simulation

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1660
Author(s):  
Ziqi Cui ◽  
Xianglin Zhou ◽  
Qingbo Meng
Keyword(s):  
Molecular Dynamics ◽  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Particle System ◽  
Fabrication Process ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Al Alloy ◽  
Laser Fabrication ◽  
Solute Atoms

This article deals with a Ti-Al alloy system. Molecular dynamics simulation was used to simulate and explore the mass transfer behavior during the laser fabrication process at atomic scale. The research goal is to investigate the mass transfer mechanism at atomic scale and the movement of solute atoms during the laser fabrication process. The mean square displacement (MSD), radial distribution function (RDF), atomic number density, and atomic displacement vector were calculated to characterize it. The results show that the TiAl alloy is completely melted when heated up to 2400 K, and increasing the temperature past 2400 K has little effect on mass transfer. As the heating time increases, the diffusion coefficient gradually decreases, the diffusion weakens, and the mass transfer process gradually stabilizes. In Ti-Al binary alloys, the diffusion coefficients of different solute atoms are related to the atomic fraction. During the melting process, the alloy particle system has a greater diffusion coefficient than the elemental particle system.

Mass Transfer at Atomic Scale in MD Simulation of Friction Stir Welding

2016 ◽  
Vol 683 ◽  
pp. 626-631 ◽  
Author(s):  
Ivan Konovalenko ◽  
Igor S. Konovalenko ◽  
Andrey Dmitriev ◽  
Serguey Psakhie ◽  
Evgeny A. Kolubaev
Keyword(s):  
Molecular Dynamics ◽  
Mass Transfer ◽  
Friction Stir Welding ◽  
Molecular Dynamics Simulation ◽  
Md Simulation ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Friction Stir ◽  
Embedded Atom ◽  
Atom Potential

Mass transfer has been studied at atomic scale by molecular dynamics simulation of friction stir welding and vibration-assisted friction stir welding using the modified embedded atom potential. It was shown that increasing the velocity movement and decreasing the angle velocity of the tool reduce the penetration depth of atoms into the opposite crystallite in the connected pair of metals. It was shown also that increasing the amplitude of vibrations applied to the friction stir welding tool results in increasing the interpenetration of atoms belonging to the crystallites joined

Momentum Removal to Obtain the Position-Dependent Diffusion Constant in Constrained Molecular Dynamics Simulation

2021 ◽  
Author(s):  
Kazushi Fujimoto ◽  
Tetsuro Nagai ◽  
Tsuyoshi Yamaguchi
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Mass Velocity ◽  
Center Of Mass ◽  
Heterogeneous Systems ◽  
Diffusion Constant ◽  
Dynamics Simulation ◽  
Coulombic Interaction ◽  
Ewald Method ◽  
Theoretical Predictions

<div>The position-dependent diffusion coefficient along with free energy profile are important parameters needed to study mass transport in heterogeneous systems such as biological and polymer membranes, and molecular dynamics (MD) calculation is a popular tool to obtain them. Among many methodologies, the Marrink-Berendsen (MB) method is often employed to calculate the position-dependent diffusion coefficient, in which the autocorrelation function of the force on a fixed molecule is related to the friction on the molecule. However, the diffusion coefficient is shown to be affected by the period of the removal of the center-of-mass velocity, which is necessary when performing MD calculations using the Ewald method for Coulombic interaction. We have clarified theoretically in this study how this operation affects the diffusion coefficient calculated by the MB method, and the theoretical predictions are proven by MD calculations. Therefore, we succeeded in providing guidance on how to select an appropriate the period of the removal of the center-of-mass velocity in estimating the position-dependent diffusion coefficient by the MB method. This guideline is applicable also to the Woolf-Roux method.</div>

Molecular Dynamics Simulation Study of the Effect of Ni, Fe, Cu on Cryolite Molten Salt System 78% Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%-Al2O3

2021 ◽  
Vol 1026 ◽  
pp. 39-48
Author(s):  
Han Bing He ◽  
Yu Si Wang ◽  
Ze Xiang Luo ◽  
Jing Zeng
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Molten Salt ◽  
Diffusion Mechanism ◽  
Research Work ◽  
Dynamics Simulation ◽  
Salt System ◽  
Electrolyte System ◽  
Aluminum Composite ◽  
Molten Salt System

The effect of different additives Ni, Fe, Cu on the structure and properties of electrolyte system 78% Na3AlF6- -9.5%AlF3-5.0%CaF2-7.5%Al2O3 at 1200K and 1.01Mpa was studied by molecular dynamics method. The radial distribution function, coordination number, diffusion coefficient, conductivity, and viscosity of the system were discussed in detail. The results demonstrated that the order of the self-diffusion coefficient of ions in the electrolyte system is: Na+ > F- > O2- > Ca2+ >Al3+. The addition of Ni and Fe connected the free aluminum composite ion groups in the system through fluorine bridges, which enhanced the interaction between Al3+ and Al3+. The addition of Cu weakened the interaction between Al3 + and Al3+ and the F-. The interaction between Al3+ and Na+, [AlF7]4- ionic groups might appeared in the melt system. After adding NiO, Fe2O3, and Cu, the electrical conductivity of the system increased, and the viscosity decreased. The research work revealed the influence of Ni, Fe, Cu on the ion existence form, mobility, inter-ion interaction and diffusion mechanism of cryolite molten salt system, which has important guiding significance for aluminum electrolysis production.

scholarly journals Comparative Studies on Water Self-Diffusivity Confined in Graphene Nanogap: Molecular Dynamics Simulation

2016 ◽  
Author(s):  
Mohammad Moulod ◽  
Gisuk Hwang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Surface Energy ◽  
Water Transport ◽  
Surface Interactions ◽  
Bulk Water ◽  
Water Desalination ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Interatomic Potentials

Fundamental understanding of the water in graphene is crucial to optimally design and operate the sustainable energy, water desalination, and bio-medical systems. A numerous atomic-scale studies have been reported, primarily articulating the surface interactions (interatomic potentials) between the water and graphene. However, a systematic comparative study among the various interatomic potentials is rare, especially for the water transport confined in the graphene nanostructure. In this study, the effects of different interatomic potentials and gap sizes on water self-diffusivity are investigated using the molecular dynamics simulation at T = 300 K. The water is confined in the rigid graphene nanogap with the various gap sizes Lz = 0.7 to 4.17 nm, using SPC/E and TIP3P water models. The water self-diffusivity is calculated using the mean squared displacement approach. It is found that the water self-diffusivity in the confined region is lower than that of the bulk water, and it decreases as the gap size decreases and the surface energy increases. Also, the water self-diffusivity nearly linearly decreases with the increasing surface energy to reach the bulk water self-diffusivity at zero surface energy. The obtained results provide a roadmap to fundamentally understand the water transport properties in the graphene geometries and surface interactions.

Multiscale Investigation of Thickness Dependent Melting Thresholds of Nickel Film Under Femtosecond Laser Heating

2018 ◽  
Author(s):  
Pengfei Ji ◽  
Mengzhe He ◽  
Yiming Rong ◽  
Yuwen Zhang ◽  
Yong Tang
Keyword(s):  
Molecular Dynamics ◽  
Femtosecond Laser ◽  
Multiscale Simulation ◽  
Nickel Film ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Model Description ◽  
Temperature Model ◽  
Laser Material Processing ◽  
Two Temperature

A multiscale modeling that integrates electronic scale ab initio quantum mechanical calculation, atomic scale molecular dynamics simulation, and continuum scale two-temperature model description of the femtosecond laser processing of nickel film at different thicknesses is carried out in this paper. The electron thermophysical parameters (heat capacity, thermal conductivity, and electron-phonon coupling factor) are calculated from first principles modeling, which are further substituted into molecular dynamics and two-temperature model coupled energy equations of electrons and phonons. The melting thresholds for nickel films of different thicknesses are determined from multiscale simulation. Excellent agreement between results from simulation and experiment is achieved, which demonstrates the validity of modeled multiscale framework and its promising potential to predict more complicate cases of femtosecond laser material processing. When it comes to process nickel film via femtosecond laser, the quantitatively calculated maximum thermal diffusion length provides helpful information on choosing the film thickness.

scholarly journals Investigation of the Effects of Adsorbed Water on Adhesion Energy and Nanostructure of Asphalt and Aggregate Surfaces Based on Molecular Dynamics Simulation

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2339 ◽  
Author(s):  
Wentian Cui ◽  
Wenke Huang ◽  
Bei Hu ◽  
Jiawen Xie ◽  
Zhicheng Xiao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Relative Concentration ◽  
Asphalt Mixture ◽  
Free Water ◽  
Adsorbed Water ◽  
Adhesion Energy ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Damage Resistance ◽  
Water Damage

The purpose of this study was to investigate the effect of aggregate surface adsorbed water on the adhesive capacity and nanostructure of asphalt-aggregate interfaces at the atomic scale. Molecular dynamics (MD) simulation was performed to measure and analyze the molecular interactions of asphalt binder with calcite and silica. Radial distribution function (RDF) and relative concentration (RC) were applied to characterizing the concentrations and distributions of asphalt components on aggregate surfaces. In addition, debonding energy and adhesion energy were employed to calculate the variations of interface adhesion energy of the asphalt-aggregate system under different conditions. The obtained results illustrated that the water molecules adsorbed onto the surface of weakly alkaline aggregates inhibited the concentration and distribution of asphalt components near the aggregate surface, decreased adhesion energy between asphalt and aggregates, and changed asphalt nanostructure. Especially, when external free water intruded into the interface of the asphalt-calcite system, the adsorbed water interacted with free water and seriously declined the water damage resistance of the asphalt mixture with limestone as an aggregate and decreased the durability of the mixtures. The water adsorbed onto the surface of the acid aggregate negatively affected the asphalt-silica interface system and slightly reduced the water damage resistance of the asphalt mixture.

Magnetorheological finishing of silicon for nanometric surface generation: An experimental and simulation study

2018 ◽  
Vol 29 (11) ◽  
pp. 2456-2464 ◽  
Author(s):  
Neha Khatri ◽  
Suman Tewary ◽  
Xavier J Manoj ◽  
Harry Garg ◽  
Vinod Karar
Keyword(s):  
Molecular Dynamics ◽  
Surface Roughness ◽  
Surface Quality ◽  
Surface Finish ◽  
Atomic Scale ◽  
Dynamics Simulation ◽  
Surface Generation ◽  
Magnetorheological Finishing ◽  
X Ray ◽  
Finishing Process

Silicon mirrors are essential for guiding the X-ray beam and focusing it to a specific location. These mirrors using total internal reflection require super smooth surface finish due to small wavelength of X-ray. Magnetorheological finishing is a computer-controlled technique used in the production of high-quality optical lenses. This process utilizes polishing slurries based on magnetorheological fluids, whose viscosity changes with the change in magnetic field. In this work, polishing potential of silicon mirrors by magnetorheological finishing process is examined to achieve nanometric surface finish for X-ray applications. The individual effect of parameters such as magnetizing current, working gap, rotational speed on surface roughness is investigated, and optimized parameters are identified. To investigate the physical essence underlying magnetorheological finishing process, the molecular dynamics simulations are used. Molecular dynamics simulation is used to study the atomic-scale removal mechanism of single-crystalline silicon in magnetorheological finishing process and attention is paid to study the effect of gap between the tool and the workpiece on surface quality. The outcome is promising and the final surface roughness achieved is as low as 6.4 nm. The surface quality is analyzed in terms of arithmetic roughness, power spectral density, and image analysis of scanning electron microscopy for uniform evaluation.

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