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.

Molecular Dynamics Study of the Effect of Dopant Atoms on Grain Boundary Sliding

2005 ◽  
Vol 903 ◽  
Author(s):  
Paul Christopher Millett ◽  
R. Panneer Selvam ◽  
Ashok Saxena
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Coincident Site Lattice ◽  
Atomic Radius ◽  
Grain Boundary Sliding ◽  
Interface Shear ◽  
Embedded Atom ◽  
Boundary Sliding ◽  
Dopant Atoms ◽  
Dynamics Simulations

AbstractMolecular dynamics simulations are used to study grain boundary sliding in pure and doped Cu bicrystals using both Lennard-Jones and Embedded-Atom Method potentials. Two tilt [100] grain boundaries are considered: the coincident site lattice Σ5 interface and a random high angle interface. Shear stress between 0.69 GPa and 1.61 GPa was applied to the bicrystals for a duration of 10 ps at ambient temperature (300K) and high temperature (800K). For the pure bicrystals, the sliding of the Σ5 interface with respect to the random interface was lower at 800K and higher at 300K. For the doped bicrystals, interstitial dopant atoms and substitutional dopant atoms with larger atomic radius were effective in retarding grain boundary sliding. These simulations will aid further work to determine how segregated dopant atoms alter the tensile properties of nanocrystalline metals.

scholarly journals On the deformation-induced grain rotations in gradient nano-grained copper based on molecular dynamics simulations

2021 ◽  
Vol 10 (1) ◽  
pp. 87-98
Author(s):  
Jiarui Zhang ◽  
Fan Yang ◽  
Yaping Liu ◽  
Zheng Zhong ◽  
Jinfeng Zhao
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Molecular Dynamics Simulations ◽  
Grain Boundary Sliding ◽  
Effect Of Temperature ◽  
Uniaxial Deformation ◽  
Grain Rotation ◽  
Activation Theory ◽  
Boundary Sliding ◽  
Dynamics Simulations

Abstract In this paper, the mechanical behavior of gradient nano-grained copper under uniaxial deformation was investigated using molecular dynamics simulations. The stress response was found to be different in the regions with different grain sizes, which was attributed to the different dislocation activities due to the dislocation-grain boundary synergies. The phenomenon of grain rotation was observed and a program was developed to accurately evaluate the grain rotation and explore its dependence on the grain size and the initial crystal orientation. It is found that all grains tend to rotate to the 30° orientation, consistent with the activation theory of the slip systems under the uniaxial deformation. The rotation magnitude is larger for larger grains, but the rotation rate is more diversely distributed for smaller grains, indicating more disturbance from grain boundary mechanisms such as the grain boundary sliding and the grain boundary diffusion for smaller grains. The effect of temperature on the grain rotation is also investigated, showing an increase of the dispersion of grain rotation distribution with the increase of temperature. This paper aims at providing insights into the synergistic deformation mechanisms from dislocations and grain boundaries accounting for the exceptional ductility of the gradient nano-grained metals.

scholarly journals Grain Boundary Relaxation in Bi-Crystals: Mechanical Spectroscopy and Molecular Dynamics Simulations

2015 ◽  
Vol 60 (1) ◽  
pp. 377-380 ◽  
Author(s):  
A.-K. Maier ◽  
D. Mari ◽  
I. Tkalcec ◽  
R. Schaller
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Molecular Dynamics Simulations ◽  
Grain Boundary Sliding ◽  
External Stress ◽  
Mechanical Spectroscopy ◽  
Relaxation Strength ◽  
Boundary Relaxation ◽  
Boundary Sliding ◽  
Dynamics Simulations

Abstract Different Au-Ag-Cu samples have been studied by mechanical spectroscopy. Both polycrystals and bi-crystals show a relaxation peak at 800 K, accompanied by an elastic modulus change. Since this peak is absent in single crystals it is related to the presence of grain boundaries. Molecular dynamics simulations reveal two microscopic mechanisms, when a shear stress is applied onto a Σ5 grain boundary: at 700 K, the boundary migrates perpendicularly to the boundary plane under an external stress. At 1000 K, only sliding at the boundary is observed. These two mechanisms acting in different temperature intervals are used to model the mechanic response of a polycrystal under an applied stress. The models yield expressions for the relaxation strength Δ and for the relaxation time τ as a function of the grain size. A comparison with the mechanical spectroscopy measurements of polycrystals and the bi-crystals show that the grain boundary sliding model reproduces correctly the characteristics of the grain boundary peak.

scholarly journals Grain Boundary Motion under Dynamic Loading: Mechanism and Large-Scale Molecular Dynamics Simulations

2013 ◽  
Vol 1 (4) ◽  
pp. 220-227 ◽  
Author(s):  
Christian Brandl ◽  
Timothy C. Germann ◽  
Alejandro G. Perez-Bergquist ◽  
Ellen K. Cerreta
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Molecular Dynamics Simulations ◽  
Dynamic Loading ◽  
Large Scale ◽  
Boundary Motion ◽  
Dynamics Simulations ◽  
Grain Boundary Motion

A Model for the Effects of Strain Rate and Temperature on the Deformation Behavior of Ultrafine-Grained Metals

2011 ◽  
Vol 291-294 ◽  
pp. 1173-1177
Author(s):  
Zi Ling Xie ◽  
Lin Zhu Sun ◽  
Fang Yang
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Boundary Diffusion ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Dislocation Slip ◽  
Deformation Response ◽  
Ultrafine Grained ◽  
Boundary Sliding

A theoretical model is developed to account for the effects of strain rate and temperature on the deformation behavior of ultrafine-grained fcc Cu. Three mechanisms, including dislocation slip, grain boundary diffusion, and grain boundary sliding are considered to contribute to the deformation response simultaneously. Numerical simulations show that the strain rate sensitivity increases with decreasing grain size and strain rate, and that the flow stress and tensile ductility increase with either increasing strain rate or decreasing deformation temperature.

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.

Temperature Dependence of Compressive Deformation Behavior of Mg89Zn4Y7 Extruded LPSO-Phase Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 607-610 ◽  
Author(s):  
Koji Hagihara ◽  
Akihito Kinoshita ◽  
Yuya Sugino ◽  
Michiaki Yamasaki ◽  
Yoshihito Kawamura ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Deformation Behavior ◽  
Grain Boundary Sliding ◽  
Deformation Mechanisms ◽  
Petch Relationship ◽  
Lpso Phase ◽  
Boundary Sliding

Deformation mechanisms of Mg89Zn4Y7 (at.%) extruded alloy, which is mostly composed of LPSO-phase, was investigated focusing on their temperature dependence. The yield stress of as-extruded alloy showed extremely high value of ~480 MPa at RT, but it largely decreased to ~130 MPa at 300 °C. The decreasing rate of the yield stress could be significantly reduced, however, by the annealing of specimen at 400 °C, by suppressing the microyielding which is considered to occur related by the grain boundary sliding in restricted regions. The yield stress of the annealed specimens with random textures could be estimated by the Hall-Petch relationship by regarding the length of long-axis of plate-like grains as a grain size between RT and 300 °C. The yield stress of the annealed specimens maintained high values even at 200°C, but it also showed large decreases at 300 °C.

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