Two grain boundaries were investigated by means of high-resolution transmission electron microscopy. The orientations of the grains were tilted by 3.1 or 2.1° from the ideal  = 3 orientation on the common tilt axis, <110>. Both boundaries were found to be asymmetrical. They dissociated into 2 parallel sub-boundaries which were separated by a thin (about 1nm) layer of faulted 9R type. One of the sub-boundaries contained 2 well-defined types of structural unit, which were referred to here as kites and rhombi. The other resembled a low-angle boundary and consisted of a row of partial dislocations. Atomistic simulations were made of  = 3, symmetrical  = 451 and asymmetrical  = 451 boundaries by using molecular dynamics and statics. On this basis, it was possible to interpret the observed structures in terms of structural units and DSC dislocations and to explain the occurrence and width of the faulted 9R phase.

D.Hofmann, M.W.Finnis: Acta Metallurgica et Materialia, 1994, 42[10], 3555-67