Numerical Analysis on Growth of Grain Boundary Cavity under Lattice Diffusion Creep

To date, analytical study has not been conducted on the growth of grain boundary cavity under lattice diffusion creep, though the growth behavior has been intensely analyzed for grain boundary diffusion creep. In this study, the growth of periodic cavities along a grain boundary is numerically simulated by obtaining a finite element solution of the Laplace equation which governs the atom flux in the grains under lattice diffusion creep. It is found that the chemical potential on the cavity surface is higher than that in the grain boundary ahead of the cavity tip. This implies that the cavity growth is stable and it maintains quasi-equilibrium shape due to the efflux of atoms from the cavity surface to the grain boundary due to the lattice diffusion. The growth rate of the cavity diameter decelerates as the cavity grows in the early stage of a/W <0.3 (a : cavity half lengtn. W : half distance between adjacent cavities) ; it is almost constant in the middle stage of 0.3<a/W<0.6,and accelerates in 0.6