Nucleation and growth of 1011 compression twin in Mg single crystals

XY Li and YF Guo and Y Mao and XZ Tang, INTERNATIONAL JOURNAL OF PLASTICITY, 158, 103437 (2022).

DOI: 10.1016/j.ijplas.2022.103437

The 1011 compression twin is more commonly observed under a-axis tension rather than c-axis compression in hexagonal close-packed (hcp) Mg single crystals both in experiments and atom-istic simulations. In this work, molecular dynamics simulations are applied to investigate the nucleation and growth of 1011 twin in Mg single crystal, which is crucial for a comprehensive understanding of the plasticity of hcp metals. A 1011 twin embryo with 4-layer height is found to be naturally nucleated at the free surface via (a) dislocation slip in Mg single crystal. The nucleation of the 1011 twin embryo involves the cross-slip of the nucleated prismatic (a) dislocation onto pyramidal 1011 plane, which is achieved by slip of (a) dislocation and shear along the (1012) direction. Basal stacking faults (SFs) forms in twin embryo and grows with the migration of 1011 twin boundary. The formation of basal SFs in 1011 twin embryo can greatly reduce the required atomic shuffling in (1210) direction, thus facilitate the development of a 1011 twin embryo. The basal SFs inside 1011 twin are anomalous SFs without dislo-cation activities involved, thus the 1011 twinning shear is not influenced by the existence of basal SFs, which is consistent with the irrational shear of 2-layer twinning dislocation.

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