GLIDING OF BOUNDARY DISLOCATIONS ON COINCIDENCE BOUNDARIES

Gliding of boundary dislocations on coincidence boundaries in Al has been investigated by in-situ straining. In the initial stages of straining, glide of a/2<110> dislocations on a {111} twin plane and their eventual pile-up at a boundary triple point were observed. During further straining, cracking along the twin boundary and emission of many dislocations from the triple point into the next grain were also observed. On the (1•13)A. or (•113)B twin boundary in σ11 relationship, two sets of dislocations were observed. One set of dislocations (M) had the Burgers vector a/2[110]AB or (a/22[74•1]A + a/22[471]A = a/22[74l]B + a/22[47•1]B) and were observed to glide at a fairly high speed on the boundary. The Burgers vector of the other set of dislocations (S) which were found to be sessile was concluded to be a/ll[l•13]A = a/11[•113]B. Furthermore, the height of the step associated with these S dislocations was estimated to be about 20Å. Finally, probability of boundary sliding at room temperature is discussed. © 1979 American Society for Metals and The Metallurgical Society of AIME.