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

A metastable β Ti–10V–3Fe–3Al–0.27O (wt.%) alloy was subjected to thermo-mechanical processing to induce α and ω 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, 101, 102 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 α′′ martensite formation, where mechanical {332}〈113〉β twinning and deformation-induced ω 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 101 s−1 or higher; it was found that the dominant deformation mode was twinning. These results have been correlated with the β phase stability of the samples.

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