Twinning and De-twinning via Glide and Climb of Twinning Dislocations along Serrated Coherent Twin Boundaries in Hexagonal-close-packed Metals

The ((1) over bar 012) twin boundaries experimentally observed in hexagonal-close-packed metals are often serrated rather than fully coherent. These serrated coherent twin boundaries (SCTBs) consist of sequential ((1) over bar 012) coherent twin boundaries and parallel basal-prismatic planes serrations (BPPS). We demonstrated that the formation of BPPS is geometrically and energetically preferred in the SCTBs, and an SCTB thus migrates by glide and climb of twinning dislocations, combined with atomic shuffling. Particularly, the climb mechanism, combined with the density and the height of BPPSs in the SCTBs, could be crucial in controlling twinning and de-twinning, and twinning-associated hardening.