Formation of zigzag-shaped {1 1 2}〈1 1 1〉 β mechanical twins in Ti–24.5 Nb–0.7 Ta–2 Zr–1.4 O alloy

Zigzag-shaped {1 1 2}〈1 1 1〉 mechanical twins are formed in a cold-compressed Ti–24.5 Nb–0.7 Ta–2 Zr–1.4 O β alloy. The formation process involves a 1/2〈1 1 1〉 screw dislocation dissociation, movement of three partials on adjacent {1 1 2} planes to form microtwins, constriction of blocked extended dislocation to form a new screw dislocation, as well as cross-slip of such dislocation onto another {1 1 2} plane in repetitive sequences. Obstacles to extended dislocation and appropriate stacking fault energy of the β phase should be the key factors for the formation of such twins.