Deformation Twinning of Molecular Dynamics Simulation in a Ternary Titanium Alloy under Nanoindentation

2016 ◽  
Vol 874 ◽  
pp. 328-332
Author(s):  
Si Ling Huang ◽  
Zhen Yu Zhang ◽  
Jun Feng Cui ◽  
Song Yang ◽  
Xiao Guang Guo
Keyword(s):  
Molecular Dynamics ◽  
Single Crystal ◽  
Md Simulations ◽  
Deformation Twinning ◽  
Dynamics Simulation ◽  
Single Element ◽  
Face Centered Cubic ◽  
Ti Alloy ◽  
Large Area ◽  
Face Centered

Nanotwinned (nt) metals exhibit excellent mechanical, electrical and thermal properties, and therefore attract much attentions. To fabricate large area nt surface, the fundamental mechanisms of deformation twinning induced by molecular dynamics (MD) are necessary to be explored. Nevertheless, MD of nt metals currently focus mainly on nt copper (Cu) and other single element metals with face-centered cubic (fcc) structure. In addition, MD simulations are usually performed on a built nt model, rather than from a single crystal, due to the difficulty of forming nanotwins. In this study, a single crystal is constructed in a ternary titanium (Ti) alloy with hexagonal closed-packed (hcp) lattice cell. Deformation twinning of MD simulation is performed in a ternary Ti alloy under nanoindentation from the built single crystal. Zonal structure is found during loading under nanoindentation, and nanograins transforms into nanotwins. Deformation twinning is significant to understanding the formation of nanotwins, as well as fabricating large area nt surface on a Ti alloy.

A Study on the Uniaxial Tension of FCC Metals at Nano Level Using MD

2008 ◽  
Vol 32 ◽  
pp. 255-258
Author(s):  
Bohayra Mortazavi ◽  
Akbar Afaghi Khatibi
Keyword(s):  
Molecular Dynamics ◽  
Uniaxial Tension ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Face Centered Cubic ◽  
Engineering Strain ◽  
Fcc Metals ◽  
Engineering Stress ◽  
Nano Science ◽  
Face Centered

Molecular Dynamics (MD) are now having orthodox means for simulation of matter in nano-scale. It can be regarded as an accurate alternative for experimental work in nano-science. In this paper, Molecular Dynamics simulation of uniaxial tension of some face centered cubic (FCC) metals (namely Au, Ag, Cu and Ni) at nano-level have been carried out. Sutton-Chen potential functions and velocity Verlet formulation of Noise-Hoover dynamic as well as periodic boundary conditions were applied. MD simulations at different loading rates and temperatures were conducted, and it was concluded that by increasing the temperature, maximum engineering stress decreases while engineering strain at failure is increasing. On the other hand, by increasing the loading rate both maximum engineering stress and strain at failure are increasing.

scholarly journals Crystallographic and Geometric Factors in the Shear Development in FCC Single Crystals: Molecular Dynamics Simulation and Experimental Study

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 666
Author(s):  
Dmitry Lychagin ◽  
Andrey Dmitriev ◽  
Anton Nikonov ◽  
Ekaterina Alfyorova
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Single Crystal ◽  
Single Crystals ◽  
Dynamics Simulation ◽  
Face Centered Cubic ◽  
Geometric Factors ◽  
Face Centered ◽  
Deformation Patterns ◽  
Shear Planes

An approach to the study of the mechanisms of shear deformation in the bulk of face centered cubic (FCC) single crystals based on molecular dynamics simulation is proposed. Similar shear patterns obtained experimentally, and in simulations, allow consideration of the effect of crystallographic and geometric factors on deformation mechanisms. Deformation of <001> single-crystal samples in the form of tetragonal prisms with {110} and {100} lateral faces and different height-to-width ratios was studied. The simulation showed that the sample vertices are the preferential sites for shear initiation. It was found that the formation of deformation domains and interaction of shear planes are caused by the geometry of shear planes in the bulk of the single crystal, i.e., by their location in relation to basic stress concentrators and by their orientations relative to the lateral faces. The deformation patterns obtained in the simulations were in good agreement with those observed in the experiments. The fractions of sliding dislocations and dislocation barriers were determined for different materials, taking into account the crystallographic and geometric factors.

Molecular Dynamics Simulation of the Solidification of Liquid Nickel Nanowires

2007 ◽  
Vol 121-123 ◽  
pp. 1053-1056
Author(s):  
Guo Rong Zhong ◽  
Qiu Ming Gao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Face Centered Cubic ◽  
Liquid Nickel ◽  
Cooling Rates ◽  
Final Structure ◽  
Embedded Atom ◽  
Nickel Nanowires ◽  
Face Centered

Molecular dynamics simulation of the solidification behavior of liquid nickel nanowires has been carried out based on the embedded atom potential with different cooling rates. The nanowires constructed with a face-centered cubic structure and a one-dimensional (1D) periodical boundary condition along the wire axis direction. It is found that the final structure of Ni nanowires strongly depend on the cooling rates during solidification from liquid. With decreasing cooling rates the final structure of the nanowires varies from amorphous to crystalline via helical multi-shelled structure.

Molecular Dynamics Simulation of Dislocation-Obstacle Interactions in Irradiated Materials

2007 ◽  
Vol 345-346 ◽  
pp. 947-950 ◽  
Author(s):  
Hyon Jee Lee ◽  
Jae Hyeok Shim ◽  
Brian D. Wirth
Keyword(s):  
Molecular Dynamics ◽  
Specific Interaction ◽  
Dislocation Motion ◽  
Dynamics Simulation ◽  
Face Centered Cubic ◽  
Void Size ◽  
Dislocation Interaction ◽  
Stacking Fault Tetrahedron ◽  
Face Centered ◽  
Induced Defects

The interactions of a dislocation with commonly observed irradiation induced defects such as a stacking fault tetrahedron (SFT) and a void are studied using molecular dynamics (MD) simulation methods. The simulation of an SFT interacting with a dislocation in face centered cubic (FCC) copper (Cu) reveals that an SFT is a strong obstacle against a dislocation motion, with dislocation detachment often involving an Orowan like mechanism. The resulting SFT generally involves a shear step, although partial absorption is also observed in some specific interaction geometries. Dislocation interaction with a void has been studied in body centered cubic (BCC) molybdenum (Mo). The dislocation locally annihilates upon contact with the void and then re-nucleates on the void surface as the dislocation glides past the void. The interaction results in the simple shear of the void by one Burger’s vector. The obstacle strength of the void is measured using conjugate gradient molecular statics (MS) method as a function of void size. A large increase in the obstacle strength is observed for a void size greater than 3 nm in diameter.

Molecular Dynamics Simulation of the Variation in the Microstructure of a Polycrystalline Material under Tensile Load

2017 ◽  
Vol 748 ◽  
pp. 375-380 ◽  
Author(s):  
Takuya Uehara
Keyword(s):  
Molecular Dynamics ◽  
External Load ◽  
Crystal Orientation ◽  
Tensile Load ◽  
Edge Length ◽  
Dynamics Simulation ◽  
Polycrystalline Materials ◽  
Face Centered Cubic ◽  
Face Centered ◽  
Dynamics Simulations

Molecular dynamics simulations were carried out to investigate the change in the crystal orientation of polycrystalline materials placed under an external load. Two models were prepared, both comprising four grains but with different grain arrangements. Each grain had a face-centered cubic structure with (001) face on the x-y plane, whereas each grain had a different rotation of orientation around the z-axis. A tensile load was applied by extending the edge length in the y direction while the other directions were kept stress-free. As a result, a significant change in the microstructure was observed, with changes in both crystal orientation and shape along with the formation of subgrains. The structure and direction of the grain boundary against the external load were also found to affect the change in the microstructure.

Structural transition and glass-forming ability of the Ni–Hf system studied by molecular dynamics simulation

2004 ◽  
Vol 19 (12) ◽  
pp. 3547-3555 ◽  
Author(s):  
J.H. Li ◽  
L.T. Kong ◽  
B.X. Liu
Keyword(s):  
Molecular Dynamics ◽  
Solid Solution ◽  
Molecular Dynamics Simulation ◽  
Solid Solutions ◽  
Dynamic Properties ◽  
Glass Forming Ability ◽  
Dynamics Simulation ◽  
Face Centered Cubic ◽  
Glass Forming ◽  
Face Centered

A tight-binding Ni–Hf potential is constructed by fitting some of the ground-state properties, such as the cohesive energy, lattice constants, and the elastic constants of some Ni–Hf alloys. The constructed potential is verified to be realistic by reproducing some static and dynamic properties of the system, such as the melting points and thermal expansion coefficients for the pure Ni and Hf as well as some of the equilibrium compounds, through molecular dynamics simulation. Applying the constructed potential, molecular dynamics simulations are performed to compare the relative stability of the face-centered-cubic (fcc)/hexagonal close-packed (hcp) solid solutions to their disordered counterparts as a function of solute concentration. It is found that the solid solutions become unstable and transform into the disordered states spontaneously, when the solute concentrations exceed the two critical solid solubilities, i.e., 25 at.% Ni for hcp Hf-rich solid solution and 18 at.% Hf for fcc Ni-based solid solution, respectively. This allows us to determine that the glass-forming ability/range of the Ni–Hf system is within 25–82 at.% Ni. Interestingly, simulations also reveal for the first time, that two mixed regions exist in which an amorphous phase coexists with a crystalline phase, and at about 18 at.% Ni, the hcp lattice turns into a new metastable phase identified to be face-centered orthorhombic structure.

Molecular dynamics simulation of screw dislocation interaction with stacking fault tetrahedron in face-centered cubic Cu

2007 ◽  
Vol 22 (10) ◽  
pp. 2758-2769 ◽  
Author(s):  
Hyon-Jee Lee ◽  
Jae-Hyeok Shim ◽  
Brian D. Wirth
Keyword(s):  
Molecular Dynamics ◽  
Screw Dislocation ◽  
Stacking Fault ◽  
Dynamics Simulation ◽  
Face Centered Cubic ◽  
Dislocation Interaction ◽  
Complete Absorption ◽  
Stacking Fault Tetrahedron ◽  
Face Centered ◽  
Dynamics Simulations

The interaction of a gliding screw dislocation with stacking fault tetrahedron (SFT) in face-centered cubic (fcc) copper (Cu) was studied using molecular dynamics simulations. Upon intersection, the screw dislocation spontaneously cross slips on the SFT face. One of the cross-slipped Shockley partials glides toward the SFT base, partially absorbing the SFT. At low applied stress, partial absorption produces a superjog, with detachment of the trailing Shockley partial via an Orowan process. This leaves a small perfect SFT and a truncated base behind, which subsequently form a sheared SFT with a pair of opposite sense ledges. At higher applied shear stress, the ledges can self-heal by gliding toward an SFT apex and transform the sheared SFT into a perfect SFT. However, complete absorption or collapse of an SFT (or sheared SFT) by a moving screw dislocation is not observed. These observations provide insights into defect-free channel formation in deformed irradiated Cu.

Deformation Mechanisms of Nanocrystalline Hexagonal Close-Packed Metals

2006 ◽  
Vol 924 ◽  
Author(s):  
Guangping Zheng
Keyword(s):  
Deformation Twinning ◽  
Dynamics Simulation ◽  
Deformation Mechanisms ◽  
Face Centered Cubic ◽  
Transformation Mechanism ◽  
Shockley Partial Dislocation ◽  
Hexagonal Close Packed ◽  
Simulation Results ◽  
Face Centered ◽  
Fcc Structure

ABSTRACTUsing molecular dynamics simulation of nanocrystalline (nc) samples with grain size of 10 nm, a reverse martensitic transformation from hexagonal close-packed (hcp) to face-centered cubic (fcc) structure is observed in nc-cobalt and nc-zirconium undergoing plastic deformation. In nc-cobalt hcp-to-fcc transformation is prevalent and deformation twinning is rarely observed. The transformation mechanism involves the motion of Shockley partial dislocation 1/3<1100> in every other (0001)hcp /(111)fcc plane. In nc-zirconium the hcp-to-fcc transformation competes with the deformation twinning. From the simulation results, it is suggested that the interaction among partials should be considered to understand the deformation mechanisms of hcp nc metals.

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