Computational Investigation of Interfacial Cracks Changes of TiAl Alloy

2017 ◽  
Vol 727 ◽  
pp. 93-97
Author(s):  
Gen Zong Song ◽  
Lin Zhang
Keyword(s):  
Molecular Dynamics ◽  
Tial Alloy ◽  
Average Energy ◽  
Causative Factor ◽  
Heating Process ◽  
Experimental Conditions ◽  
Embedded Atom ◽  
Interfacial Cracks ◽  
Dynamics Calculation ◽  
Dynamics Simulations

In an effort to develop into a practical application of TiAl alloys for aerospace materials, Researchers at home and abroad in the use of alloying and thermal processing methods to improve the brittleness and other areas a lot of work.The existence of cracks which led to the kinds of material degradation of the major causative factor. However, it is difficult for us to observed the change of the local atom structure of the material by experiments in the limitation from our experimental conditions, nevertheless, computational research provide us the possibility that we can observe the evolution of the structure. Molecular dynamics calculation is considered to be well suited to describe the change of potential energy of the atoms in such a system. Embedded atom method (EAM) and canonical ensemble (NVT) molecular dynamics simulations have been carried out to obtain pre-cracks of different lengths of the structure of TiAl alloy. According to the average energy of atoms and the radial density distribution function, with increasing temperature the changes, analysis of TiAl alloy films of micro-cracks in the heating process, the structure changes with temperature.

Molecular Dynamics Investigation of Relaxation and Local Structure Changes in a Quenched Molten TiAl Alloy Film

2010 ◽  
Vol 650 ◽  
pp. 324-329
Author(s):  
Lin Zhang ◽  
Qin Na Fan ◽  
Cai Bei Zhang ◽  
Shao Qing Wang
Keyword(s):  
Molecular Dynamics ◽  
Local Structure ◽  
Tial Alloy ◽  
Mean Square Displacement ◽  
Alloy Film ◽  
Distribution Functions ◽  
Relaxation Processes ◽  
Embedded Atom ◽  
Structure Changes ◽  
Dynamics Simulations

Relaxation and local structure changes of a molten TiAl alloy film during quenching have been investigated by molecular dynamics simulations within the framework of embedded atom method (EAM). The details of atom motions are analyzed using mean square displacement (MSD). Accompanying with massive atom rearrangement at a certain quenched temperature and time, local structural patterns are identified by decomposing peaks of pair distribution functions (PDFs) according to the pair analysis(PA) technique. The relaxation factor clearly reveals two relaxation processes involving in slow relaxation and fast relaxation of the quenched liquid TiAl film. Concerning the studied film, the obtained results reveal how quenched temperatures affect local structure changes.

Molecular Dynamics Simulation of Sputtering with Mmany-Body Interactions

1988 ◽  
Vol 100 ◽  
Author(s):  
Davy Y. Lo ◽  
Tom A. Tombrello ◽  
Mark H. Shapiro ◽  
Don E. Harrison
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Single Crystal ◽  
Low Energy ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Many Body ◽  
Embedded Atom ◽  
Dynamics Simulations ◽  
Small Single Crystal

ABSTRACTMany-body forces obtained by the Embedded-Atom Method (EAM) [41 are incorporated into the description of low energy collisions and surface ejection processes in molecular dynamics simulations of sputtering from metal targets. Bombardments of small, single crystal Cu targets (400–500 atoms) in three different orientations ({100}, {110}, {111}) by 5 keV Ar+ ions have been simulated. The results are compared to simulations using purely pair-wise additive interactions. Significant differences in the spectra of ejected atoms are found.

An Atomistic Study of Hydrogen Effects on the Fracture of Tilt Boundaries in Nickel.

1991 ◽  
Vol 238 ◽  
Author(s):  
N. R. Moody ◽  
S. M. Foiles
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Site Occupancy ◽  
Boundary Structure ◽  
Trap Site ◽  
Embedded Atom ◽  
Defect Sites ◽  
Tilt Boundaries ◽  
Temperature Exposure ◽  
Dynamics Simulations

ABSTRACTIn this study, molecular dynamics simulations were used to fracture Σ9 tilt boundaries in nickel lattices containing a range of trap site hydrogen concentrations. These lattices were created in a previous study using Monte Carlo simulations and the Embedded Atom Method to duplicate room temperature exposure to a hydrogen environment. The molecular dynamics simulations were run at absolute zero to immobilize the hydrogen distributions for determination of trap site occupancy effects on grain boundary fracture. In all lattices, fracture began by the breaking of bonds next to polyhedral defect sites that characterize the boundary structure followed by rapid failure of the remaining bonds. The effect of hydrogen was to lower the stress for fracture from 18 GPa to a lower limiting value of 8 GPa as the trap sites along the boundary plane filled. The simulations showed that the atoms at these sites were the only atoms involved in the fracture process. Within the constraints imposed on these calculations, the results of this study showed that the ‘inherent’ effect of hydrogen in the absence of plastic deformation is to reduce the cohesive force between atoms across the boundary.

Study on the structural transition of CoNi nanoclusters using molecular dynamics simulations

2018 ◽  
Vol 32 (11) ◽  
pp. 1850133
Author(s):  
J. H. Xia ◽  
Xue-Mei Gao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Structural Transition ◽  
Correction Function ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Analysis Technique ◽  
Dynamics Simulations ◽  
Embedded Atom Method Potential ◽  
Pair Analysis

In this work, the segregation and structural transitions of CoNi clusters, between 1500 and 300 K, have been investigated using molecular dynamics simulations with the embedded atom method potential. The radial distribution function was used to analyze the segregation during the cooling processes. It is found that Co atoms segregate to the inside and Ni atoms preferably to the surface during the cooling processes, the Co[Formula: see text]Ni[Formula: see text] cluster becomes a core–shell structure. We discuss the structural transition according to the pair-correction function and pair-analysis technique, and finally the liquid Co[Formula: see text]Ni[Formula: see text] crystallizes into the coexistence of hcp and fcc structure at 300 K. At the same time, it is found that the frozen structure of CoNi cluster is strongly related to the Co concentration.

scholarly journals Deformation Behavior of Nanocrystalline Body-Centered Cubic Iron with Segregated, Foreign Interstitial: A Molecular Dynamics Study

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5351
Author(s):  
Ahmed Tamer AlMotasem ◽  
Matthias Posselt ◽  
Tomas Polcar
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Deformation Behavior ◽  
Large Scale ◽  
Grain Boundary Sliding ◽  
Carbon And Nitrogen ◽  
Embedded Atom ◽  
Boundary Sliding ◽  
Dynamics Simulations

In the present work, modified embedded atom potential and large-scale molecular dynamics’ simulations were used to explore the effect of grain boundary (GB) segregated foreign interstitials on the deformation behavior of nanocrystalline (nc) iron. As a case study, carbon and nitrogen (about 2.5 at.%) were added to (nc) iron. The tensile test results showed that, at the onset of plasticity, grain boundary sliding mediated was dominated, whereas both dislocations and twinning were prevailing deformation mechanisms at high strain. Adding C/N into GBs reduces the free excess volume and consequently increases resistance to GB sliding. In agreement with experiments, the flow stress increased due to the presence of carbon or nitrogen and carbon had the stronger impact. Additionally, the simulation results revealed that GB reduction and suppressing GBs’ dislocation were the primary cause for GB strengthening. Moreover, we also found that the stress required for both intragranular dislocation and twinning nucleation were strongly dependent on the solute type.

Effects of Hydrogen on the Fracture Properties of Σ9 and Σ11 Tilt Boundaries in Nickel

1992 ◽  
Vol 278 ◽  
Author(s):  
J.E. Angelo ◽  
W.W. Gerberich ◽  
N.R. Moody ◽  
S.M. Foiles
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Fracture Stress ◽  
Equilibrium Distribution ◽  
Embedded Atom Method ◽  
Far Field ◽  
Fracture Properties ◽  
Embedded Atom ◽  
Tilt Boundaries ◽  
Dynamics Simulations

AbstractIn this study, the Embedded Atom Method is combined with Monte Carlo and molecular dynamics simulations to study the fracture properties of Σ9 and Σ11 tilt boundaries in nickel. The Monte Carlo simulations are used to simulate the exposure of the bicrystal to a hydrogen environment at 300° C. These simulations establish the equilibrium distribution of hydrogen at the boundaries as a function of far-field concentration. The effect of the hydrogen on the fracture process is then studied with molecular dynamics. It will be shown that the fracture stress of the Σ9 boundary is affected over a wider range of far-field concentrations than the Σ11 boundary, although the Σ11 boundary shows that catastrophic failure occurs when the sample is charged beyond a certain far-field concentration.

Molecular Dynamics Simulation of Relaxation and Local Structure Change of a Molten Cu135 Cluster during Rapidly Quenching

2011 ◽  
Vol 694 ◽  
pp. 908-913 ◽  
Author(s):  
S.N Xu ◽  
N. He ◽  
L. Zhang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Local Structure ◽  
Average Energy ◽  
Dynamics Simulation ◽  
Relaxation Processes ◽  
Quenching Temperature ◽  
Embedded Atom ◽  
Structure Changes ◽  
Β Relaxation

Relaxation and local structure changes of a molten Cu135 cluster have been studied by molecular dynamics simulation using embedded atom method when the cluster is rapidly quenched to 700K, 600K, 500K, 400K, 300K, 200K, and 100K. With decreasing quenching temperature, details of energy evolvement and relaxation are analyzed. The simulation results show that the final structures are molten at 700K, like-icosahedral geometry at 600K-200K, non-crystal at 100K. The average energy of atoms is the lowest at 500K, and in the relaxation has abrupt increase at 25,135 and 42ps separately at 400K, 300K, and 200K. The simulation reveals that the quenching temperature has great affect on the relaxation processes of the Cu135 cluster after β relaxation region.

Molecular Dynamics Prediction of the Influence of Composition on Thermotransport in Ni-Al Melts

2017 ◽  
Vol 12 ◽  
pp. 93-110 ◽  
Author(s):  
Tanvir Ahmed ◽  
Elena V. Levchenko ◽  
Alexander V. Evteev ◽  
Zi Kui Liu ◽  
William Yi Wang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Interatomic Potential ◽  
Diffusion In Solids ◽  
Recent Experimental Study ◽  
Heat Of Transport ◽  
Embedded Atom ◽  
Rich Liquid ◽  
Predicted Values ◽  
Dynamics Simulations ◽  
Embedded Atom Method Potential

The influence of composition on thermotransport (coupling between mass and heat transport) in Ni-Al melts is investigated by making use of equilibrium molecular dynamics simulations in conjunction with the Green-Kubo formalism. To describe interatomic interactions in Ni-Al melt models, we employ the embedded-atom method potential developed in [G.P. Purja Pun, Y. Mishin, Phil. Mag., 2009, 89, 3245]. It is demonstrated that the employed interatomic potential gives good agreement with the recent experimental study [E. Sondermann, F. Kargl, A. Meyer, Presented at the 12th International Conference on Diffusion in Solids and Liquids (DSL-2016), 26-30 June 2016, Split, Croatia] regarding the direction of thermotransport in Al-rich liquid Ni-Al alloys. Moreover, the predicted values of the reduced heat of transport (the quantity which explicitly characterizes both the magnitude and direction of thermotransport) in Ni-Al melts, reveal fairly weak composition dependence while being practically independent of temperature at all. Accordingly, in the presence of a temperature gradient, our simulation results for the models of liquid Ni25Al75, Ni50Al50 and Ni75Al25 alloys predict consistently Ni and Al to migrate to the cold and hot ends, respectively. Meanwhile, the highest value, about eV, of the reduced heat of transport is observed for Ni50Al50 alloy model and it slightly decreases towards Al-rich and Ni-rich compositions.

scholarly journals Molecular Dynamics Studies of the Melting of Copper with Vacancies amd Dislocations at High Pressures

MRS Advances ◽  
2017 ◽  
Vol 2 (48) ◽  
pp. 2597-2602 ◽  
Author(s):  
Clarence C Matthai ◽  
Jessica Rainbow
Keyword(s):  
Molecular Dynamics ◽  
Melting Temperature ◽  
Large Scale ◽  
High Pressures ◽  
Defect Density ◽  
Melting Process ◽  
Interatomic Potentials ◽  
Embedded Atom ◽  
Line Defects ◽  
Dynamics Simulations

ABSTRACTMolecular dynamics simulations of the melting process of bulk copper were performed using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) with the interatomic potentials being described by the embedded atom method. The aim of the study was to understand the effects of high pressures and defects on the melting temperature. The simulations were visualised using Visual Molecular Dynamics (VMD). The melting temperature of a perfect copper crystal, was found to be slightly higher than the experimentally observed value. The melting temperature as a function of pressure was determined and compared with experiment. Point and line defects, in the form of dislocations, were then introduced into crystal and the new melting temperature of the crystal determined. We find that the melting temperature decreases as the defect density is increased. Additionally, the slope of the melting temperature curve was found to decrease as the pressure was increased while the vacancy formation energy increases with pressure.

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