Characterization of Microstructure of Deformation Twin Boundary in Zinc by Transmission Electron Microscopy

The microstructure of 10\bar 12 twin boundary in zinc induced by severe plastic deformation was characterized using transmission electron microscope (TEM). The result showed that the actual twin boundary can deviate significantly from the theoretical twinning plane. By high resolution TEM analysis, the actual twin boundaries consist of (10\bar 12 ) coherent twin boundary (CTB) connected with short BP/PB facets, or only consist of a series of BP/PB facets perpendicular to each other. These two kinds of twin boundaries with different microstructures can coexist stably in a 10\bar 12 twin. Based on the dislocation theory, the migration mechanism of these two kinds of twin boundaries was discussed. For the first kind of twin boundary, the migration can be accomplished via the motion of twinning dislocation on the CTB together with the motion of interface dislocation on the BP/PB facets. For the second kind of twin boundary, the migration is accomplished via a unit cell reconstruction mechanism. The coexistence of the two kinds of twin boundaries can be explained based on the nucleation and growth process of a 10\bar 12 twin.