Stress induced grain boundary motion

We investigated the motion of planar symmetrical and asymmetrical tilt boun daries in high-purity aluminium with < 112 >- and < 111 > -tilt axes under the influence of an external mechanical stress field. It was found that the motion of low-angle grain boundaries as well as high-angle grain boundarie s can be induced by the imposed external stress. The observed activation en thalpies allow conclusions on the migration mechanism of the grain boundary motion. The motion of planar low- and high-angle grain boundaries under th e influence of a mechanical stress field can be attributed to the movement of the grain boundary dislocations which comprise the structure of the boun dary. A sharp transition between low-angle grain boundaries and high-angle grain boundaries was observed at 13.6 degrees, which was apparent from a st ep of the activation enthalpy for the grain boundary motion. For the invest igated boundaries the transition angle was independent of tilt axis, impuri ty content and tilt boundary plane. (C) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.