On dislocation involvement in Ti-Nb gum metal plasticity

The excellent mechanical properties of the Ti-Nb-based gum metal were originally proposed to arise from a dislocation-free giant fault mechanism; however, the involvement of lattice dislocations in the process is still under debate. To address this issue, gum metal deformation mechanisms are investigated systematically on cast specimens, employing postmortem and in situ analysis techniques. The results demonstrate that a giant fault mechanism (which appears to be a phase-transformation-assisted nanotwinning mechanism) governs gum metal plasticity without direct assistance from dislocations during the process. (c) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.