GRAIN-BOUNDARIES DURING SUPERPLASTIC DEFORMATION

The structure and properties of grain boundaries are considered during superplastic deformation on the basis of recent concepts of the interaction between lattice dislocations and grain boundaries. It is shown that the boundaries contain both, lattice and grain boundary dislocations. The presence of these extraneous defects leads to an increase of grain boundary energy; there is an increase of the vacancy concentration and enhancement of the diffusion coefficient in the boundaries with non‐equilibrium structure. The results of numerical estimation of dislocation density and of the change in diffusion parameters agree well with the established experimental data. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA