ON THE CONTRIBUTION OF EXTRINSIC GRAIN-BOUNDARY DISLOCATIONS TO GRAIN-BOUNDARY SLIDING IN BICRYSTALS

The possibility of separating the contributions of extrinsic grain bou ndary dislocations of different origins to the overall grain boundary shear is shown using the model of grain boundary sliding operating und er the conditions of plastic incompatibility. The approach suggested i s applied to the case of deformation of incompatible zinc bicrystals w ith a 29 degrees[<10(1)over bar 0>] symmetric tilt boundary which is c lose to the Sigma = 15{<1(2)over bar 11>} coincidence boundary. Quanti tative estimates of contributions of extrinsic grain boundary dislocat ions to grain boundary sliding and intragranular strain in the vicinit y of the boundary are obtained. (C) 1997 Acta Metallurgica Inc.