On the $\left(10\bar{1}2\right)$ twinning growth mechanism in hexagonal close-packed metals

Highlights: • The controversy between TD mechanism and shuffling mechanism is raised in explaining $\left(10\bar{1}2\right)$ TB departing from K1 plane. • BP/PB interfaces can accommodate the deviations, thus $\left(10\bar{1}2\right)$ twinning growth is still ascribed to TD. • Based on the track record of publishing on $\left(10\bar{1}2\right)$ twinning, a few scientific problems and further works on twinning in HCP metals are propose. Besides coordinating plastic deformation, the frequently observed $\left(10\bar{1}2\right)$ twins can cause the change of microstructure and texture of hexagonal close-packed (HCP) metals, influencing the mechanical properties. Thus, understanding $\left(10\bar{1}2\right)$ twinning mechanism is essential. In this paper, we review the recent basic research on $\left(10\bar{1}2\right)$ twinning growth process by experiments, modeling and theory. The structural characterization of $\left(10\bar{1}2\right)$ twinning boundaries and exploring $\left(10\bar{1}2\right)$ twinning growth mechanism are summarized in detail. Finally, for this research topic, a few critical scientific problems and further works on deformation twinning in HCP metals are proposed.