Energy-Minimizing Structures For Low-Angle Grain Boundaries in Zinc

Dislocation models for low angle grain boundaries have been widely known since 1950 and the proposed structures have been extensively confirmed by transmission electron microscopy, although most studies have been confined to the cubic metals. A generalization of the earlier geometrical work, known as the 0-lattice, represents the state of the art in predicting grain boundary structures on a purely geometrical basis, but the analysis is always predicated on the assumption that grain boundaries are basically planar defects. In some work on precipitation in the Al-Zn-Mg system Vanderwalker and Vander Sande observed non-planar low angle grain boundaries, although these may have been the results of pinning by embryonic precipitates or other solute interaction effects: we have observed non-planar boundaries in pure zinc where no such pinning effects are available to explain the puckering.