Why are {10(1)over-bar2} twins profuse in magnesium?

We show that {10 (1) over bar2} twinning in magnesium acts as an effective sink of basal dislocations without loss of mobility. The lattice dislocation decomposes into the b(0/0)(BP) dislocation recently identified by the present authors, and a residual dislocation. The b(0/0)(BP) dislocation in turn spontaneously decomposes into a Burgers vector content of the basal-prismatic facet related disclination dipole, f(0)(BP), plus an associated number of twinning disconnections. The residual dislocation lies on the basal-prismatic facet and thus remains glissile should the twin boundary move forward or recede back. Importantly, the basal-prismatic facet absorbs any twinning disconnection gliding on one side of the twin boundary and releases another one to other side, thereby enabling the twin boundary to progress through a forest of basal dislocations with no apparent decrease in mobility or loss of coherency. This mechanism explains why {10 (1) over bar2} twinning is profuse in hexagonal close-packed metals as slip induces the interfacial atomic structure to change favorably for twin propagation. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.