Extended core of twinning disconnection associated with {112‾2} twinning

{112¯2} twinning is widely activated in α-titanium (α-Ti) to accommodate the strain along the c -axis. The short, three-layer height bands are observed along {112¯2} twin boundary, but the formation mechanism and atomic structure of these bands are in debate. In this work, we characterized atomic structure of these bands by using high-angle annular dark-field scanning transmission electron microscopy. Combining with topological analysis and first-principles density functional theory calculations, our conclusion is that these bands have a distorted ω-phase structure. The formation of the distorted ω-structure can be treated as the dissociations of a three-layer twinning disconnection ( b ₃ , 3h_{112‾2}), where a leading partial disconnection (1/2 b ₃ , 3h_{112¯2}) and a trialing partial disconnection (1/2 b ₃ , 3h_{112¯2}) are bounded by a distorted ω-structure. Correspondingly, we proposed possible mechanisms for twin thickening via partial disconnections. These findings enhance the fundamental understanding of twinning behavior in hexagonal metals.