Atomic-scale study of {112} twin boundary structure in a β-Ti alloy

The atomic structure of {112} twin boundary in a specialty beta-Ti alloy, gum metal, has been studied by means of conventional transmission electron microscopy, bright-field and high-angle annular dark field scanning transmission electron microscopy imaging. The observations provide direct evidence that the {112} twin boundary has a complex, multiple-layer structure, which is composed of various structural units. These structural units are formed as a result of different degrees of inner atomic-column shifting. The complex structure of the {112} twin boundary is different to the atomic structure of the previously reported omega phase.