Abstract :
It is now recognized that grain boundary sliding (GBS) is often an important mode of
deformation in polycrystalline materials. This paper reviews the developments in GBS over the
last four decades including the procedures available for estimating the strain contributed by
sliding to the total strain, ξ , and the division into Rachinger GBS in conventional creep and
Lifshitz GBS in diffusion creep. It is shown that Rachinger GBS occurs under two distinct
conditions in conventional creep depending upon whether the grain size, d, is larger or smaller
than the equilibrium subgrain size, λ. A unified model is presented leading to separate rate
equations for Rachinger GBS in power-law creep and superplasticity. It is demonstrated that
these two equations are in excellent agreement with experimental observations. There are
additional recent predictions, not fully resolved at the present time, concerning the role of GBS
in nanostructured materials. C 2006 Springer Science + Business Media, Inc.
