Anelasticity Study on Motions of Atoms in the Grain Boundary Regions in Nanocrystalline Gold

概要

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High-density nanocrystalline (n-) Au was prepared by the gas deposition method. Various anelastic and plastic creep processes associated with the grain boundary (GB) regions were observed. The vibrating reed measurements at 102 Hz with strain amplitude of 10−6 show a very broad internal friction peak near 95 K, Qp,95 K−1, and a steep increase in the anelastic strain above 200 K, εa-I,>200 K. The tensile tests show a steep increase in the anelastic strain above 200 K, εa-II,>200 K, for the stress beyond a few MPa and a linear plastic creep strain above 200 K, εpc-1, for stress range between 30 MPa and 150 MPa. The activation parameters, 1⁄τ0 of 3×1011 s−1 and E of 0.16 eV, are found for Qp,95 K−1, where τ0 and E are a pre-exponential factor and an activation energy of the relaxation time τ. We surmise that simple relaxation processes are responsible for Qp,95 K−1. The values of 1⁄τ0 and E found for εa-I,>200 K and εa-II,>200 K decrease with increasing the applied stress or the temperature, indicating that their atomic processes are the same feather. Further, E found for εpc-1 is similar to or slightly smaller than that of εa-II,>200 K. These observations indicate that the atomic motions in the GB regions of n-Au develop in scale in the order of the underlying processes for εa-I,>200 K, εa-II,>200 K and εpc-1, and are so different from those in the conventional polycrystalline Au.
Japan Institute of Metalsの論文
2003-01-01