Observations of dislocations in [011] symmetrical tilt boundaries near Σ9 C.S.L. in aluminium

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Abstract
SUMMARY: Bicrystals with [011] symmetrical tilt boundaries rotated 36° have been examined by transmission electron microscopy. The boundary which was near a (41) plane showed networks of structural grain boundary dislocations. Possible vectors were derived from Bollmanns coincident site lattice theory for the nearest C.S.L., i.e. Σ9. The networks have been examined in a number of reflections and are considered to be composed of dislocations with b2 (i.e. 1/9 [12]) and b3 (1/6 [121] or 1/18 [127]) vectors. Four b3 vectors can change from one to the other by interactions with other structural dislocations. Evidence of iron additions reducing the mobility of dislocations is presented, and evidence of lattice dislocation dissociations are discussed. The mobility of dislocations in this Σ9 C.S.L. boundary is compared with a Σ27 coincidence lattice.