Deformation Twinning in Octahedron-Based Face-Centered Cubic Metallic Structures: Localized Shear-Force Dipoles Drive Atomic Displacements

Using the correlative method of unsymmetrized self-consistent field we study the dynamical properties of anharmonic crystals, namely, the quadratic correlations between atomic displacements from the equilibrium positions and their mean square relative displacements in anharmonic crystals. In the present paper we calculate these values for a weakly anharmonic crystals with the face-centered cubic lattice in which the nearest neighbors interact. The second order of the method enables one to calculate for this lattice the correlations between the nearest, second, third and fourth neighbors. The results are compared with those obtained previously for simplified models. The dependence on the coordination number and on the dimensionality of the lattice is discussed.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.874.328 ◽

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.

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Deformation Mechanisms of Nanocrystalline Hexagonal Close-Packed Metals

MRS Proceedings ◽

10.1557/proc-0924-z03-19 ◽

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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