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Research Papers

The Influence of Lattice Misfit on the Atomic Structures and Defect Energetics of Face Centered Cubic–Body Centered Cubic Interfaces

[+] Author and Article Information
X.-Y. Liu, R. G. Hoagland, M. Nastasi, A. Misra

 Los Alamos National Laboratory, Los Alamos, NM 87545

M. J. Demkowicz

 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139

J. Eng. Mater. Technol 134(2), 021012 (Mar 27, 2012) (6 pages) doi:10.1115/1.4005920 History: Received September 09, 2011; Revised January 04, 2012; Published March 26, 2012; Online March 27, 2012

Using “tunable” interatomic potentials, the lattice misfits for a fcc–bcc metal system have been varied in atomistic models, while keeping other properties essentially unchanged. The procedure and the fitting results of such tunable interatomic potentials for fcc–bcc systems are presented. Varying lattice misfits were found to significantly alter the atomic structure of fcc–bcc interfaces in Kurdjumov–Sachs crystallographic orientation. Defect formation energies at the interfaces were calculated. For vacancies, in general, high numbers of low energy sites are associated with high dislocation junction densities. For interstitials, the formation energies are all substantially below the bulk value, regardless of lattice misfits. These results are relevant to understanding the sink strength of interfaces with different atomic structures.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

The relaxed KS interface atomic structure with lattice misfits χ =afcc /abcc , (a) 1.043, (b) 1.095 (Cu–Nb), (c) 1.152, (d) 1.185, (e) 1.225, and (f) 1.346. The horizontal axis is in [11 2¯]fcc ||[1 1¯2]bcc (or x) direction. The vertical axis is in [1 1¯0]fcc ||[ 1¯11]bcc (or z) direction. The interface direction [111]fcc ||[110]bcc (or y direction) is out of the paper. Only fcc and bcc atoms adjacent to the interface are shown. In (a)–(d), the coloring of atoms are mapped to the excess potential energies of each atoms. In (e)–(f), yellow (green) or light grey colors in each figure denotes Cu (Ag) or bcc atoms, respectively. Also, in (a)–(c), a parallelogram is marked to indicate the quasi-unit-cell at the KS interfaces. (For interpretation of the references to colors in this figure, the reader is referred to the web version of this article.)

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Figure 2

(a) Schematic of interface structure showing a representative portion of the quasi-unit-cell at KS interface where the candidate defect sites were taken from and (b) Cu vacancy formation energetics at the interface. The horizontal axis is the index number of defect sites from the quasi-unit-cell at the KS interface. All are in the case of misfit ratio χ = 1.185. The vacancy formation energy of Cu bulk is also shown in (b)

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Figure 3

The cumulative distribution of interfacial fcc sites as a function of the vacancy formation energies, for all six lattice misfits considered in this study. For comparison, the vacancy formation energies of Cu and Ag bulk are also shown

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Figure 4

The fraction of interfacial fcc sites by the energetic criteria ( Evf≤Evf (bulk)  − ΔE) is plotted as a function of the lattice misfit ratio and compared to the area density of misfit dislocation junctions at the interface.

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Figure 5

The cumulative distribution of interfacial fcc sites as a function of the interstitial formation energies, for all six lattice misfits considered in this study. For comparison, the interstitial formation energies of Cu and Ag bulk are also shown.

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