Atomic Mechanisms of Grain Boundary Motion

2005 ◽  
Vol 502 ◽  
pp. 157-162 ◽  
Author(s):  
A. Suzuki ◽  
Yuri M. Mishin
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Geometric Model ◽  
Lattice Rotation ◽  
Shear Stresses ◽  
Translation Rate ◽  
Embedded Atom ◽  
Local Lattice ◽  
Symmetrical Tilt ◽  
Grain Boundary Motion

We present results of atomistic computer simulations of spontaneous and stress-induced grain boundary (GB) migration in copper. Several symmetrical tilt GBs have been studied using the embedded-atom method and molecular dynamics. The GBs are observed to spontaneously migrate in a random manner. This spontaneous GB motion is always accompanied by relative translations of the grains parallel to the GB plane. Furthermore, external shear stresses applied parallel to the GB and normal to the tilt axis induce GB migration. Strong coupling is observed between the normal GB velocity vn and the grain translation rate v||. The mechanism of GB motion is established to be local lattice rotation within the GB core that does not involve any GB diffusion or sliding. The coupling constant between vn and v|| predicted within a simple geometric model accurately matches the molecular dynamics observations.

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.

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

An Experimental and Computational Study of the Elastic-Plastic Transition in Thin Films

2001 ◽  
Vol 673 ◽  
Author(s):  
Erica T. Lilleodden ◽  
Jonathan A. Zimmerman ◽  
Stephen M. Foiles ◽  
William D. Nix
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Computational Study ◽  
Strong Dependence ◽  
Embedded Atom Method ◽  
Shear Stresses ◽  
Gradient Plasticity ◽  
Embedded Atom ◽  
Low Dislocation Density ◽  
Dislocation Sources

ABSTRACTNanoindentation studies of thin metal films have provided insight into the mechanisms of plasticity in small volumes, showing a strong dependence on the film thickness and grain size. It has been previously shown that an increased dislocation density can be manifested as an increase in the hardness or flow resistance of a material, as described by the Taylor relation [1]. However, when the indentation is confined to very small displacements, the observation can be quite the opposite; an elevated dislocation density can provide an easy mechanism for plasticity at relatively small loads, as contrasted with observations of near-theoretical shear stresses required to initiate dislocation activity in low-dislocation density materials. Experimental observations of the evolution of hardness with displacement show initially soft behavior in small-grained films and initially hard behavior in large-grained films. Furthermore, the small-grained films show immediate hardening, while the large grained films show the ‘softening’ indentation size effect (ISE) associated with strain gradient plasticity. Rationale for such behavior has been based on the availability of dislocation sources at the grain boundary for initiating plasticity. Embedded atom method (EAM) simulations of the initial stages of indentation substantiate this theory; the indentation response varies as expected when the proximity of the indenter to a Σ79 grain boundary is varied.

scholarly journals Molecular Dynamics Study of Thermal Disorder in a Bicrystal Model

1991 ◽  
Vol 229 ◽  
Author(s):  
Tue Nguyen ◽  
Paul S. Ho ◽  
Thomas Kwok ◽  
Cynthia Nitta ◽  
Sidney Yip
Keyword(s):  
Molecular Dynamics ◽  
Theoretical Analysis ◽  
Interfacial Region ◽  
Embedded Atom Method ◽  
Continuous Transition ◽  
Embedded Atom ◽  
Complete Melting ◽  
Order Energy ◽  
Thermal Disorder ◽  
Symmetrical Tilt

AbstractThis work studies a (310) θ = 36.86° <001> symmetrical-tilt bicrystal model using an Embedded Atom Method aluminum potential. Based on explicit results obtained from the simulations regarding structural order, energy, and mobility, we find that our bicrystal model shows no evidence of pre-melting (complete melting below Tm). Both the surface and the grain-boundary interface exhibit thermal disorder at temperatures below Tm, with complete melting occurring only at, or very near, Tm. Concerning the details of the onset of melting, the data show considerable disordering in the interfacial region starting at about 0.93 Tm. The interfaces exhibit metastable behavior in this temperature range, and the temperature variation of the interfacial thickness suggests that the disordering induced by the interface is a continuous transition, a behavior that has been predicted by a theoretical analysis.

scholarly journals High Fidelity Polycrystalline CdTe/CdS Heterostructures via Molecular Dynamics

MRS Advances ◽  
2017 ◽  
Vol 2 (53) ◽  
pp. 3225-3230 ◽  
Author(s):  
Rodolfo Aguirre ◽  
Jose J. Chavez ◽  
Xiaowang Zhou ◽  
David Zubia
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Small Region ◽  
Composition Analysis ◽  
Cross Sectional ◽  
Solar Cell Efficiency ◽  
Cell Efficiency ◽  
Cds Film ◽  
Dynamics Simulations ◽  
Grain Boundary Motion

ABSTRACTMolecular dynamics simulations of polycrystalline growth of CdTe/CdS heterostructures have been performed. First, CdS was deposited on an amorphous CdS substrate, forming a polycrystalline film. Subsequently, CdTe was deposited on top of the polycrystalline CdS film. Cross-sectional images show grain formation at early stages of the CdS growth. During CdTe deposition, the CdS structure remains almost unchanged. Concurrently, CdTe grain boundary motion was detected after the first 24.4 nanoseconds of CdTe deposition. With the elapse of time, this grain boundary pins along the CdS/CdTe interface, leaving only a small region of epitaxial growth. CdTe grains are larger than CdS grains in agreement with experimental observations in the literature. Crystal phase analysis shows that zinc blende structure dominates over the wurtzite structure inside both CdS and CdTe grains. Composition analysis shows Te and S diffusion to the CdS and CdTe films, respectively. These simulated results may stimulate new ideas for studying and improving CdTe solar cell efficiency.

Atomistic Aspects of Crack Propagation Along High Angle Grain Boundaries

1996 ◽  
Vol 460 ◽  
Author(s):  
Diana Farkas
Keyword(s):  
Grain Boundary ◽  
Atomistic Simulations ◽  
High Angle ◽  
Brittle Behavior ◽  
Embedded Atom ◽  
Tilt Boundaries ◽  
Symmetrical Tilt ◽  
Grain Boundary Fracture ◽  
Tilt Grain Boundary ◽  
Boundary Fracture

ABSTRACTWe present atomistic simulations of the crack tip configuration near a high angle Σ= 5 [001](210) symmetrical tilt grain boundary in NiAl. The simulations were carried out using molecular statics and embedded atom (EAM) potentials. The cracks are stabilized near a Griffith condition involving the cohesive energy of the grain boundary. The atomistic configurations of the tip region are different in the presence of the high angle grain boundary than in the bulk. Three different configurations of the grain boundary were studied corresponding to different local compositions. It was found that in ordered NiAl, cracks along symmetrical tilt boundaries show a more brittle behavior for Al rich boundaries than for Ni-rich boundaries. Lattice trapping effects in grain boundary fracture were found to be more significant than in the bulk.

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