Why are 10(1)over-bar2 twins profuse in magnesium?
H El Kadiri and CD Barrett and J Wang and CN Tome, ACTA MATERIALIA, 85, 354-361 (2015).
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.
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