The use of transmission electron microscopy identified 2 types of dislocation network in as-received material. Hexagonal dislocation networks that comprised 1/3<11•0>-type dislocations were observed and were attributed to interaction between parallel sets of a-type dislocations on individual prism planes. Dislocations which formed the hexagonal networks underwent a reduction in energy, and were considered to be equilibrium structures. Square dislocation networks which comprised 1/3<11•0>, [00•1], and 1/3<11•3>-type dislocations on basal, prism, and pyramidal planes were identified and were considered to be the result of parallel sets of a-type dislocations which reacted with parallel sets of c-type dislocations so as to form unstable short dislocation segments that were composed of a+c-type dislocations. Dislocations which were arranged in square networks did not result in any energy reduction and were considered to be quasi-equilibrium configurations that were more likely to dissociate or reorganize, during deformation or thermal processing, than were dislocations with hexagonal coordination.

D.A.Hoke, G.T.Gray: Scripta Metallurgica et Materialia, 1995, 33[2], 171-7