The nucleation and migration of 10(1)over-bar1 twins in hcp materials

J Ombogo and E Vitral and A Zahiri and L Cao, JOURNAL OF MATERIALS SCIENCE, 60, 6715-6734 (2025).

DOI: 10.1007/s10853-025-10844-3

10 (1) over bar1 twins are known to play a pivotal role in the deformation and fracture ofhcp materials under c-axis compression. In this paper, the nucleation and migration of 10 (1) over bar1 twins are investigated through the integration of atomistic simulations and theoretical calculations. The atomistic simulations reveal extensive nucleation of 10 (1) over bar1 twins, occurring either directly at the free surface or via a bcc intermediate state in bulk. The theoretical calculations identify the surfacenucleation as the low-shear mode with conjugate twinning plane K-2 = 10 (1) over bar3. Incontrast, the bulk- nucleation is determined as the high-shear mode with irrational twinning shear and K-2 plane. Our analyses pinpoint that their fundamental distinction lies in whether the twinning shear encompasses an < a > component along the common zone axis. During subsequent twin growth, the high-shear mode activates sequential b(2) dislocations, while the low- shear mode involves concurrent activation of two stacked b(2) dislocations, collectively forming a b(4) dislocation. This paper provides valuable insights into the critical distinctions and the complex interplay between the two 10 (1) over bar1 modes in hcp materials.

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