Transmutation of zonal twinning dislocations during non-cozone {101¯1} twin-twin interaction in magnesium

Abstract

Theoretically, a twinning dislocation must stay on the twinning plane which is the first invariant plane of a twinning mode, because the glide of twinning dislocation linearly transforms the parent lattice to the twin lattice. However, recent experimental observations showed that a $\left\{10\overline{1}1\right\}〈10\overline{1}\overline{2}〉$ twin variant could cross another variant during twin-twin interaction. It is well known that $\left\{10\overline{1}1\right\}$ twinning is mediated by zonal twinning dislocations. Thus, how the zonal twinning dislocations transmute during twin-twin interaction is of great interest but not well understood. In this work, atomistic simulation is performed to investigate interaction between $\left\{10\overline{1}1\right\}$ twin variants. Our results show that when an incoming twin variant impinges on the other which acts as a barrier, surprisingly, the barrier twin can grow at the expense of the incoming twin. Eventually one variant consumes the other. Structural analysis shows that the twinning dislocations of the barrier variant are able to penetrate the zone of twin-twin intersection, by plowing through the lattice of one variant and transform its lattice into the lattice of the other. Careful lattice correspondence analysis reveals that, the lattice transformation from one variant to the other is close to $\left\{10\overline{1}2\right\}〈10\overline{1}\overline{1}〉$ twinning, but the orientation relationship deviates by a minor lattice rotation. This deviation presents a significant energy barrier to the lattice transformation, and thus it is expected such a twin-twin interaction will increase the stress for twin growth.