The Role of Faceting in 10(1)over-bar2 Twin Nucleation

CD Barrett, MAGNESIUM TECHNOLOGY 2020, 129-134 (2020).

DOI: 10.1007/978-3-030-36647-6_21

1012 twinning is the most profuse twin mode in Mg and plays a major role in its plasticity and deformation. Identification of the mechanisms and locations of twinning nucleation is crucial to characterize the ensuing microstructural evolution and failure. Herein, we provide a new theory of hexagonal close-packed twin nucleation. In essence, the theory is that twins need a pre-existing interface upon which to grow. In the earliest stages of nucleation, this requirement implies that the twin must be able to facet onto the same plane as the local interface, whether it be a free surface, stacking fault, or grain boundary, and that the action of twinning must reduce the defect energy of the pre- existing structure in order to remain stable until it can grow large enough to emit disconnections. The theory is demonstrated on 1012 twin nucleation at grain boundaries and stacking faults in Mg via molecular dynamics.

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