When the sliding of a viscous grain boundary was accommodated by grain-boundary diffusion, the sliding rate and the stress distribution on the boundary were evaluated by using the energy-balance method developed by Mori et al. The phenomena analyzed were the sliding of non-planar grain boundaries, the sliding of boundaries containing particles and the rotation of polygonal grains in 2 dimensions. For given grain-boundary configurations or grain shapes, analytical expressions were obtained for the sliding and rotation rates, in the steady state, as a function of the viscosity for boundary sliding. The obtained sliding and rotation rates were different to the existing ones. In particular, the sliding rates of non-planar grain boundaries had expressions different to the classical predictions of Raj and Ashby. The sliding/rotation rate and the normal stress on the grain boundary decreased with increasing boundary viscosity. When the boundary viscosity became sufficiently large, the deformation rate was dominated by viscous grain-boundary sliding and the contribution of grain-boundary diffusion became negligible.

Viscous Grain-Boundary Sliding and Grain Rotation Accommodated by Grain-Boundary Diffusion. B.N.Kim, K.Hiraga, K.Morita: Acta Materialia, 2005, 53[6], 1791-8