Strain rate dependence of deformation-induced transformation and twinning in a metastable titanium alloy

A metastable beta Ti-10V-3Fe-3Al-0.27O (wt.%) alloy was subjected to thermo-mechanical processing to induce alpha and omega phase formation, so that the alloy can exhibit the features responsible for both transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) behaviour during deformation. The alloy thereafter was deformed at different strain rates (10(-3), 10(-1), 10(1), 10(2) s(-1)) at ambient temperature. At slow strain rate (<10(-3) s(-1)), in addition to slip the alloy displayed a dominant deformation mechanism with alpha '' martensite formation, where mechanical {332}< 113 >beta twinning and deformation-induced omega phase were also activated. At an intermediate strain rate, 10(-1) s(-1), there was a competition between stress-induced phase transformations and stress-induced twinning deformation mechanisms. With increasing strain rate to 10(1) s(-1) or higher; it was found that the dominant deformation mode was twinning. These results have been correlated with the beta phase stability of the samples. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.