材料期刊网

Zigzag-shaped {112}< 111 > mechanical twins are formed in a cold-compressed Ti-24.5 Nb-0.7 Ta-2 Zr-1.4 O beta alloy. The formation process involves a 1/2 < 111 > screw dislocation dissociation, movement of three partials on adjacent {112} 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 {112} plane in repetitive sequences. Obstacles to extended dislocation and appropriate stacking fault energy of the 13 phase should be the key factors for the formation of such twins. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.