Zigzag configuration of mechanical twin and stress-induced omega phase in metastable β Ti–34Nb (at.%) alloy

• Zigzag configuration of {1 1 2}〈1 1 1〉 twin and omega phase occurs in Ti–34Nb alloy.
• Zigzag configuration is formed by movement of partials and dislocation cross-slip.
• Stacking fault energy of the β phase governs the formation of zigzag configuration.

A zigzag configuration of {1 1 2}〈1 1 1〉 mechanical twin and stress-induced omega phase with habit plane of {0 −1 1 0}ω//{2 −1 −1}β was observed by TEM in a metastable β Ti–34Nb (at.%) alloy after compression at room temperature. The zigzag configuration can be formed by the movement of three-layer homogeneous 1/6〈1 1 1〉 and inhomogeneous 1/12〈1 1 1〉, 1/3〈1 1 1〉, and 1/12〈1 1 1〉 shears on consecutive {1 1 2} planes, respectively resulting from dissociation of a perfect 1/2〈1 1 1〉 screw dislocation and the cross-slip of the screw dislocation when it is blocked at the obstacle. The stacking fault energy of the β phase is a key factor for the formation of such zigzag configuration in the deformed β Ti–34Nb (at.%) alloy.