Migration of the Σ7 tilt grain boundary in Al under an applied external stress

Stress-driven migration of symmetrical tilt grain boundaries with misorientations close to 38.2 degrees < 1 1 1 >, 73.4 degrees < 2 0 1 > and 135.6 degrees < 1 1 2 > rotations related to the same special Sigma 7{1 3 2} CSL boundary was measured by in situ observations in a scanning electron microscope. Contrary to expectations and theoretical predictions, the investigated boundaries moved under an applied stress, but their motion did not produce shear. The three crystallographically equivalent Sigma 7 boundaries were found to behave differently with respect to the migration rate and its temperature dependence. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.