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Research Papers

Meta-Atom Molecular Dynamics for Studying Material Property Dependent Deformation Mechanisms of Alloys

[+] Author and Article Information
Peng Wang

Institute of Applied Mechanics,
Zhejiang University,
Hangzhou 310027, China;
Institute of Advanced Engineering Structures
and Materials,
Zhejiang University,
Hangzhou 310027, China

Hongtao Wang

Institute of Applied Mechanics,
Zhejiang University,
Hangzhou 310027, China
e-mail: htw@zju.edu.cn

1Corresponding author.

Contributed by the Applied Mechanics Division of ASME for publication in the JOURNAL OF APPLIED MECHANICS. Manuscript received July 25, 2017; final manuscript received August 16, 2017; published online September 8, 2017. Editor: Yonggang Huang.

J. Appl. Mech 84(11), 111002 (Sep 08, 2017) (8 pages) Paper No: JAM-17-1404; doi: 10.1115/1.4037683 History: Received July 25, 2017; Revised August 16, 2017

Massively parallel molecular dynamics (MD) simulations have been performed to understand the plastic deformation of metals. However, the intricate interplay between the deformation mechanisms and the various material properties is largely unknown in alloy systems for the limited available interatomic potentials. We adopt the meta-atom method proposed by Wang et al., which unifies MD simulations of both pure metals and alloys in the framework of the embedded atom method (EAM). Owing to the universality of EAM for metallic systems, meta-atom potentials can fit properties of different classes of alloys. Meta-atom potentials for both aluminum bronzes and hypothetic face-centered-cubic (FCC) metals have been formulated to study the parametric dependence of deformation mechanisms, which captures the essence of competitions between dislocation motion and twinning or cleavage. Moreover, the solid-solution strengthening effect can be simply accounted by introducing a scaling factor in the meta-atom method. As the computational power enlarges, this method can extend the capability of massively parallel MD simulations in understanding the mechanical behaviors of alloys. The calculation of macroscopic measurable quantities for engineering oriented alloys is expected to be possible in this way, shedding light on constructing materials with specific mechanical properties.

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References

Figures

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Fig. 1

(a) The fitting result to Rose’s equation from the developed meta-atom potential for Cu (refer to Sec. 3.1) and (b) the energy profile along the Bain’s transformation route (inset)

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Fig. 2

(a) The stress–strain curve of a Cu NW upon uniaxial loading at 300 K. Insets are the typical configuration at different plastic deformation stages. (b) Reorientation of Cu NW. The red colored atoms are located on twin boundaries (see color figure online).

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Fig. 3

Meta-atom potentials for aluminum bronzes: (a) the embedding functions F(ρ), (b) the pair interaction functions ϕ(r), (c) the electron density function ρ(r), and (d) the corresponding generalized planar fault curves

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Fig. 4

Snapshots of dislocation emission events by MD simulation of meta-atom Cu: (a) ε = 0.010, (b) ε = 0.019, (c) ε = 0.053, (d) ε = 0.062, (e) ε = 0.073, and (f) ε = 0.1

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Fig. 5

Snapshots of dislocation emission events by MD simulation of meta-atom Cu-6 wt % Al: (a) ε = 0.022, (b) ε = 0.025, (c) ε = 0.070, and (d) ε = 0.097

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Fig. 6

Snapshots of the cleavage process by MD simulation of a brittle hypothetic FCC metal: (a) ε = 0.037, (b) ε = 0.039, (c) ε = 0.048, and (d) ε = 0.054

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Fig. 7

(a) The generalized planar fault curves for meta-atom Cu and a brittle hypothetic FCC metal and (b) Brittle versus ductile response of constructed hypothetic FCC metals

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Fig. 8

Scaling meta-atom model. (a) Equal number of α- and β-type meta-atoms randomly occupy the FCC lattice sites; (b) The spatial distribution of Von Mises strain for the meta-atom Cu-6 wt % Al model after full relaxation. The scaling factor is set to be s = 1.1. The atomic scale Von Mises strain is calculated according to the method in Ref. [34]. (c) The probability density of Von Mises strain for the scaling factor s = 1, 1.05, and 1.1 (symbols) is well fitted by the log-normal distribution (solid lines). (d) The dependence of the mean Von Mises strain and the standard deviation on the scaling factors. (e) The change of the lattice constant and the low-index surface energies with the scaling factors. (f) The change of elastic moduli with the scaling factors.

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Fig. 9

Atomic model of an extended dislocation subjected to an applied shear stress

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Fig. 10

(a) GPF curves coincides with each other for s = 1.0 and 1.1, (b) the dependence of Peierls stress on the scaling factor, and (c) the relation between the dislocation velocity and the applied shear stress. Details about the simulation and calculation can be found in the online supporting material.

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