Evaluation of Driving Force and Mobility for Diffusion Induced Grain Boundary Migration in Ni(Cu) System

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著者

    • KAJIHARA Masanori
    • Tokyo Institute of Technology, Nagatsuta, Department of Materials Science and Engineering, Tokyo Institute of Technology

抄録

The kinetics of diffusion induced grain boundary migration (DIGM) in the Ni(Cu) system was experimentally studied by Liu <I>et al</I>. using polycrystalline Cu/Ni/Cu diffusion couples annealed at 888 K for various times between 4.8×10<sup>2</sup> and 9.36×10<sup>4</sup>s. The notation Ni(Cu) means that Cu atoms diffuse into a pure Ni or binary Ni-Cu phase. Their experimental results have been quantitatively analyzed using the energy balance model proposed by Kajihara and Gust. The face-centered-cubic (f.c.c.) solution phase in the binary Ni-Cu system is assumed to be elastically isotropic. The molar Gibbs energy of the f.c.c. phase is expressed by a subregular solution model. The migration rate <I>v</I> of the moving grain boundary is described as a function of the reaction time <I>t</I> by the equation <I>v</I>=<I>k</I>(<I>t</I>/<I>t</I><sub>0</sub>)<sup><I>m</I></sup>. Here, <I>t</I><sub>0</sub> is unit time, 1 s. From these relationships, the effective driving force Δ<sup>ef</sup><I>G</I><sub>m</sub> for DIGM has been calculated as a function of the reaction time. Although Δ<sup>ef</sup><I>G</I><sub>m</sub> monotonically decreases with increasing reaction time from the maximum value of 184 J/mol to the minimum value of 8 J/mol, it is still large enough to drive the grain boundary migration against the curvature of the moving grain boundary even at late stages of the reaction. The mobility <I>M</I> of the moving grain boundary also monotonically decreases with increasing reaction time from 2×10<sup>-17</sup> m<sup>4</sup>/J s at 4.8×10<sup>2</sup>s to 2×10<sup>-18</sup> m<sup>4</sup>/J s at 9.36×10<sup>4</sup>s. However, considering the grain boundary energy contribution due to the curvature of the moving grain boundary, <I>M</I> is supposed to be almost constant during the reaction.

収録刊行物

  • ISIJ international  

    ISIJ international 38(1), 86-92, 1998-01-15 

    The Iron and Steel Institute of Japan

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