Atomistic study of nucleation and migration of the basal/prismatic interfaces in Mg single crystals

Abstract

The formation of the basal/prismatic (BP) interfaces during nucleation and growth of a reoriented crystal in Mg single crystals under c-axis tension is investigated by molecular dynamics simulations. The BP interfaces nucleate by a shuffling mechanism via local atomic rearrangement. Both two-layer disconnection and one-layer disconnection contribute to the migration of the BP interfaces. The three-dimensional analysis reveals that the two-layer disconnection forms at the junction between the partial pyramidal dislocation and BP interface. The BP interfacial disconnections prefer to move towards the $\left[1\overline{2}10\right]$ direction rather than the $\left[\overline{1}010\right]$/[0001] direction due to the accumulation of mismatches along the $\left[\overline{1}010\right]$/[0001] direction. Moreover, the BP interface can transform to the $\left\{10\overline{1}2\right\}$ twin boundary and vice versa. The transformation from a BP interface to a twin boundary occurs through the diagonal pile-up of BP interface disconnections, and the reverse transformation involves an upright pile-up process. Both BP transformation and $\left\{10\overline{1}2\right\}$ twinning can effectively accommodate the applied tensile strain along the c-axis. The co-existing BP interfaces and $\left\{10\overline{1}2\right\}$ twin boundaries allow for large deviations of a twin interface from the $\left\{10\overline{1}2\right\}$ twin plane.