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°〈1 1 1〉, 73.4°〈2 0 1〉 and 135.6°〈1 1 2〉 rotations related to the same special Σ7{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 Σ7 boundaries were found to behave differently with respect to the migration rate and its temperature dependence.