Nucleation mechanism of {112}<111> mechanical twins in as-quenched β metastable Ti-12 wt.% Mo alloy

β-Ti alloys with plasticity driven by dislocation glide suffer from a lack of work hard-ening, which is most of the time a major drawback. Recently, several β-metastable Ti grades have been designed to exhibit simultaneous TRIP and TWIP effects in order to improve mechanical properties of as-quenched β phase. Indeed, work hardening rates never reached before by Ti alloys seem to result from the activation of α” stress-induced martensitic (SIM) phase as well as from both {332} and {112} twinning systems. Hardly any result has been reported about the activation of both twinning systems. The aim of the present study is to identify the formation mechanism as well as the role of {112}⟨111⟩ mechanical twins in the global mechanical behaviour of TRIP/TWIP titanium alloys. TEM revealed the dislocations involved in the twinning process as well as their interactions with the freshly formed mechanical twins. Also, quantitative in situ TEM tensile testing of FIB-milled samples have been performed to understand the very first steps of twin nucleation