scholarly journals Coupled atomistic-mesoscopic model of polycrystalline plasticity

2001 ◽  
Vol 677 ◽  
Author(s):  
Fabrizio Cleri ◽  
Gregorio D'Agostino ◽  
Alessandra Satta ◽  
Luciano Colombo
Keyword(s):  
Grain Boundaries ◽  
Mesoscale Model ◽  
Triple Junctions ◽  
Extended Defect ◽  
Statistical Population ◽  
Mesoscopic Model ◽  
Level Information ◽  
Defect Interactions ◽  
Dynamics Simulations ◽  
Distribution Of Dislocations

ABSTRACTWe discuss a microstructure evolution framework which couples atomic-level information about extended-defect interactions into a mesoscopic model; the latter, in turn, describes the dy-namic evolution of a statistical population of grain boundaries and dislocations. Atomistic simulations are carried out by means of molecular dynamics simulations on both isolated and interacting dislocations, grain boundaries, triple junctions, microcracks; the reference material for such studies is, at present, Silicon with the Stillinger-Weber potential. The mesoscale model describes the motion of discrete triple junctions (and, consequently, of the continuous network of adjoining grain boundaries) embedded in a continuous medium containing a homogenous, evolving distribution of dislocations.

Atomistic models of triple junctions and the origin of topological changes in microstructural evolution

2000 ◽  
Vol 652 ◽  
Author(s):  
Alessandra Satta ◽  
Luciano Colombo ◽  
Fabrizio Cleri
Keyword(s):  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Level Structure ◽  
Atomic Scale ◽  
Triple Junctions ◽  
Line Energy ◽  
Mesoscopic Models ◽  
Scale Modelling ◽  
Dynamics Simulations ◽  
Topological Changes

ABSTRACTTriple junctions are crucial elements in microstructural evolution: for example, their mobility can be rate-limiting if lower than that of grain boundaries. However, very little is known about their atomic-level structure and properties. We studied the atomic structure of multiple-twin triple junctions in silicon, formed by the convergence of two {111} and one {221} symmetric-tilt grain boundaries. Molecular dynamics simulations with the Stillinger-Weber potential and constant-traction border conditions were performed on several triple junction configurations, obtained by different combinations of the three grain boundaries. All the configurations have a positive excess line energy, a measurable volume contraction and display regions of opposite, tensile and compressive, residual stress. Moreover, we tried to elucidate the role of triple junctions as being the seeds of the only microscopic events that can lead to topological changes in the microstructure. Such events, usually dubbed T1 and T2 in mesoscopic models, correspond to grain switching (in the Ashby-Verrall sense) and grain-disappearance events, respectively. We present preliminary results for the atomic-scale modelling of both classes of topological events and discuss the connection between atomistic and mesoscopic modelling of microstructural evolution.

Molecular Dynamics Simulations of Nanocrystalline Nickel and Copper Revealing Different Failure Model of FCC Metals

2009 ◽  
Vol 633-634 ◽  
pp. 31-38
Author(s):  
Ajing Cao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Grain Boundaries ◽  
Large Scale ◽  
Uniaxial Tensile ◽  
Face Centered Cubic ◽  
Triple Junctions ◽  
Fcc Metals ◽  
Face Centered ◽  
Dynamics Simulations

We have previously reported that the fracture behavior of nanocrystalline (NC) Ni is via the nucleation and coalescence of nano-voids at grain boundaries and triple junctions, resulting in intergranular failure mode. Here we show in large-scale molecular dynamics simulations that partial-dislocation-mediated plasticity is dominant in NC Cu with grain size as small as ~ 10 nanometers. The simulated results show that NC Cu can accommodate large plastic strains without cracking or creating damage in the grain interior or grain boundaries, revealing their intrinsic ductile properties compared with NC Ni. These results point out different failure mechanisms of the two face-centered-cubic (FCC) metals subject to uniaxial tensile loading. The insight gained in the computational experiments could explain the good plasticity found in NC Cu not seen in Ni so far.

Plastic deformation of nanocrystalline copper-antimony alloys

2010 ◽  
Vol 25 (3) ◽  
pp. 411-421 ◽  
Author(s):  
Rahul K. Rajgarhia ◽  
Douglas E. Spearot ◽  
Ashok Saxena
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Grain Boundaries ◽  
Partial Dislocation ◽  
Dislocation Nucleation ◽  
Uniaxial Tensile ◽  
Triple Junctions ◽  
Dopant Atoms ◽  
Dynamics Simulations ◽  
Antimony Alloys

Molecular dynamics simulations are used to evaluate the influence of Sb dopant atoms at the grain boundaries on plastic deformation of nanocrystalline Cu. Deformation is conducted under uniaxial tensile loading, and Sb atoms are incorporated as substitutional defects at the grain boundaries. The presence of randomly dispersed Sb atoms at the grain boundaries does not appreciably influence the mechanisms associated with dislocation nucleation in nanocrystalline Cu; grain boundary ledges and triple junctions still dominate as partial dislocation sources. However, the magnitude of the tensile stress associated with the partial dislocation nucleation event does increase with increasing Sb concentration and also with increasing grain size. The flow stress of nanocrystalline Cu increases with increasing Sb concentration up to 1.0 at.% Sb, with a maximum observed at a grain size of 15 nm for all Sb concentrations (0.0–2.0 at.% Sb).

Molecular Dynamics Simulations of Shock-Defect Interactions in Two-Dimensional Nonreactive Crystals

1992 ◽  
Vol 296 ◽  
Author(s):  
Robert S. Sinkovits ◽  
Lee Phillips ◽  
Elaine S. Oran ◽  
Jay P. Boris
Keyword(s):  
Molecular Dynamics ◽  
Hexagonal Lattice ◽  
Square Lattice ◽  
Two Dimensional ◽  
Connection Machine ◽  
Defect Sites ◽  
Principal Axes ◽  
Shock Motion ◽  
Defect Interactions ◽  
Dynamics Simulations

AbstractThe interactions of shocks with defects in two-dimensional square and hexagonal lattices of particles interacting through Lennard-Jones potentials are studied using molecular dynamics. In perfect lattices at zero temperature, shocks directed along one of the principal axes propagate through the crystal causing no permanent disruption. Vacancies, interstitials, and to a lesser degree, massive defects are all effective at converting directed shock motion into thermalized two-dimensional motion. Measures of lattice disruption quantitatively describe the effects of the different defects. The square lattice is unstable at nonzero temperatures, as shown by its tendency upon impact to reorganize into the lower-energy hexagonal state. This transition also occurs in the disordered region associated with the shock-defect interaction. The hexagonal lattice can be made arbitrarily stable even for shock-vacancy interactions through appropriate choice of potential parameters. In reactive crystals, these defect sites may be responsible for the onset of detonation. All calculations are performed using a program optimized for the massively parallel Connection Machine.

Migration of grain boundaries and triple junctions in high-purity aluminum during annealing after slight cold rolling

2015 ◽  
Vol 107 ◽  
pp. 134-138 ◽  
Author(s):  
Wenhong Yin ◽  
Weiguo Wang ◽  
Xiaoying Fang ◽  
Congxiang Qin ◽  
Xiaoguang Xing
Keyword(s):  
Cold Rolling ◽  
Grain Boundaries ◽  
High Purity ◽  
Triple Junctions ◽  
High Purity Aluminum

scholarly journals Failure Mechanisms of Cu–Cu Bumps under Thermal Cycling

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5522
Author(s):  
Kai-Cheng Shie ◽  
Po-Ning Hsu ◽  
Yu-Jin Li ◽  
Dinh-Phuc Tran ◽  
Chih Chen
Keyword(s):  
Thermal Cycling ◽  
Grain Boundaries ◽  
Maximum Stress ◽  
Failure Mechanisms ◽  
Deep Understanding ◽  
Bonding Interface ◽  
Triple Junctions ◽  
Element Analysis ◽  
Resistance Change ◽  
Hybrid Joints

The failure mechanisms of Cu–Cu bumps under thermal cycling test (TCT) were investigated. The resistance change of Cu–Cu bumps in chip corners was less than 20% after 1000 thermal cycles. Many cracks were found at the center of the bonding interface, assumed to be a result of weak grain boundaries. Finite element analysis (FEA) was performed to simulate the stress distribution under thermal cycling. The results show that the maximum stress was located close to the Cu redistribution lines (RDLs). With the TiW adhesion layer between the Cu–Cu bumps and RDLs, the bonding strength was strong enough to sustain the thermal stress. Additionally, the middle of the Cu–Cu bumps was subjected to tension. Some triple junctions with zig-zag grain boundaries after TCT were observed. From the pre-existing tiny voids at the bonding interface, cracks might initiate and propagate along the weak bonding interface. In order to avoid such failures, a postannealing bonding process was adopted to completely eliminate the bonding interface of Cu–Cu bumps. This study delivers a deep understanding of the thermal cycling reliability of Cu–Cu hybrid joints.

scholarly journals Formation of a single quasicrystal upon collision of multiple grains

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Insung Han ◽  
Kelly L. Wang ◽  
Andrew T. Cadotte ◽  
Zhucong Xi ◽  
Hadi Parsamehr ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Large Scale ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Decagonal Quasicrystal ◽  
Bulk Crystal Growth ◽  
Computational Discovery ◽  
Dynamics Simulations ◽  
Novel Applications ◽  
Small Misorientation

AbstractQuasicrystals exhibit long-range order but lack translational symmetry. When grown as single crystals, they possess distinctive and unusual properties owing to the absence of grain boundaries. Unfortunately, conventional methods such as bulk crystal growth or thin film deposition only allow us to synthesize either polycrystalline quasicrystals or quasicrystals that are at most a few centimeters in size. Here, we reveal through real-time and 3D imaging the formation of a single decagonal quasicrystal arising from a hard collision between multiple growing quasicrystals in an Al-Co-Ni liquid. Through corresponding molecular dynamics simulations, we examine the underlying kinetics of quasicrystal coalescence and investigate the effects of initial misorientation between the growing quasicrystalline grains on the formation of grain boundaries. At small misorientation, coalescence occurs following rigid rotation that is facilitated by phasons. Our joint experimental-computational discovery paves the way toward fabrication of single, large-scale quasicrystals for novel applications.

Anomalous diffusion of water molecules at grain boundaries in ice Ih

2018 ◽  
Vol 20 (20) ◽  
pp. 13944-13951 ◽  
Author(s):  
Pedro Augusto Franco Pinheiro Moreira ◽  
Roberto Gomes de Aguiar Veiga ◽  
Ingrid de Almeida Ribeiro ◽  
Rodrigo Freitas ◽  
Julian Helfferich ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Grain Boundaries ◽  
Anomalous Diffusion ◽  
First Principles ◽  
Water Molecules ◽  
Diffusive Behavior ◽  
Classical Molecular Dynamics ◽  
Dynamics Simulations

First-principles and classical molecular dynamics simulations show that diffusion of water molecules at pre-melted grain boundaries in ice is glassy-like, showing sub-diffusive behavior.

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