Interface structures and twinning mechanisms of $ \{ \bar 1012\} $ twins in hexagonal metals

Abstract

A controversy concerning the description of $ \{ \bar 1012\} $ $ \langle 10\bar 11\rangle $ twinning, whether it is shear-shuffle or pure glide-shuffle or pure shuffle, has developed. There is disagreement about the interpretation of transmission electron microscopic observations, atomistic simulations and theories for twin growth. In this article, we highlight the atomic-level, characteristic, equilibrium and non-equilibrium boundaries and corresponding boundary defects associated with the three-dimensional ‘normal’, ‘forward’ and ‘lateral’ propagation of $ \{ \bar 1012\} $ growth/annealing and deformation twins. Although deformation twin boundaries (TBs) after recovery exhibit some similarity to growth/annealing TBs because of the plastic accommodation of stress fields, there are important distinctions among them. These distinctions distinguish among the mechanisms of twin growth and resolve the controversy. In addition, a new type of disconnection, a glide disclination, is described for twinning. Synchroshear, seldom considered, is shown to be a likely mechanism for $ \{ \bar 1012\} $ twinning.

Keywords

• Twin
• boundary
• disclination
• synchroshear
• hexagonal materials