Influence of long term annealing on grain boundary character distributions in nickel

Experiments were designed to study the long term annealing behaviour of commercially pure nickel. Low strain levels and moderate annealing temperatures of 700 and 800 degrees C were utilized for times up to 168 h and evaluated for special boundary percentages using electron back-scattered diffraction. The effect of extended annealing times at both temperatures was to increase substantially the percentage of special boundaries over the range, Sigma(3-29), including the twin related Sigma 3(n) types. The increase in the percentage of special boundaries was interpreted in terms of dislocation generation at grain boundaries during straining and the annealing out of these extrinsic grain boundary dislocations by climb along the grain boundaries and movement of the boundaries during the annealing process. (c) 2005 Elsevier B.V. All rights reserved.