Twin nucleation from disconnection-dense sites between stacking fault pairs in a random defect network

Deformation twinning, an important plastic deformation mode, critically influences the strength and ductility of Mg. As such, a fundamental understanding of twin nucleation will provide us with an important insight into the conditions that favor the onset of this deformation mode. To reveal the twin nucleation mechanism, we construct a defect network without making assumptions about the types and relative densities of dislocations present. The generated defect network features a high density of I1 stacking faults as well as disconnections between them. Deformation modeling results suggest that this structure enables a twin nucleation event from disconnectiondense sites between I1 stacking faults pairs. By probing twin nucleation and early-stage growth inside of the random defect network, we propose a geometry-based twin variant selection rule as well as a pure-shuffle twin nucleation and early-stage growth mechanism underpinning twinning in Mg.