Motion of 〈1 0 0〉-tilt grain boundaries

Abstract

The motion of planar symmetrical 〈1 0 0〉-tilt boundaries in high-purity aluminum was investigated in situ under the influence of an external mechanical stress field. It was observed that the motion of planar 〈1 0 0〉-tilt boundaries could be activated by an applied shear stress which acts perpendicular to the grain boundary plane. The motion of the grain boundaries is thermally activated so that we could derive the activation parameters for the motion from the in situ data of the mobility at different temperatures. A sharp transition between low angle grain boundaries and high angle grain boundaries was observed for the planar tilt boundaries at 8.6° which was apparent from a step change in the activation enthalpy for the stress induced grain boundary motion. The observed activation parameters for the stress-induced motion can be correlated to the activation parameters of self-diffusion for the motion of low angle boundaries and to the activation parameters of grain boundary diffusion for the motion of high angle grain boundaries. From these correlations, it seems obvious that the motion of planar low and high angle grain boundaries under the influence of a mechanical stress field can be attributed to the movement of the grain boundary dislocations which comprise the structure of the boundary.