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

A zigzag configuration of {112} < 111 > mechanical twin and stress-induced omega phase with habit plane of {0-110}(omega)//{2 - 1 - 1}(beta) was observed by TEM in a metastable beta Ti-34Nb (at.%) alloy after compression at room temperature. The zigzag configuration can be formed by the movement of three-layer homogeneous 1/6 < 111 > and inhomogeneous 1/12 < 111 >, 1/3 < 111 >, and 1/12 < 111 > shears on consecutive {112} planes, respectively resulting from dissociation of a perfect 1/2 < 111 > screw dislocation and the cross-slip of the screw dislocation when it is blocked at the obstacle. The stacking fault energy of the beta phase is a key factor for the formation of such zigzag configuration in the deformed beta Ti-34Nb (at.%) alloy. (C) 2014 Elsevier B.V. All rights reserved.