Structure and climb of 13 111 twin dislocations in aluminum

The structure and motion via climb of 13 111 twin dislocations along a coherent twin boundary in aluminum are examined via a combination of high resolution transmission electron microscopy (HRTEM) and computer simulation. Climb of these defects increases the thickness of the twin and is a possible alternative to the more familiar glide mechanism. Detailed analysis of the observed defect structure and comparison with atomistic modeling shows that the 13 111 twin dislocations exist in a dissociated configuration. This structure can be interpreted as the relaxation of the 13 111 dislocation into two dislocations, a Shockley partial and a stair-rod dislocation, which are separated by a short segment of stacking fault. The atomistic mechanism of the climb of the dislocations is analyzed.