Demonstrating a duplex TRIP/TWIP titanium alloy via the introduction of metastable retained β-phase
Karri Sri Naga Sesha, Kenta Yamanaka, Manami Mori, Yusuke Onuki, Shigeo Sato, Damien Fabrègue, Akihiko Chiba
Abstract
This study demonstrates transformation-induced plasticity (TRIP) in conjunction with twinning-induced plasticity (TWIP) in α + β titanium alloys by introducing metastable retained β-phase. By annealing at 850 °C followed by water quenching, metastable retained β-phase (∼25%) was obtained in Ti–6Al–4V alloy. Stress-induced phase transformation in the retained β-phase produced orthorhombic α′′-martensite associated with (021)α′′ twinning, which significantly increased the work-hardening rate and uniform elongation. The findings reveal that the minor retained β-phase is responsible for macroscopic deformation behavior and could aid in novel alloy design that can increase work hardenability with fewer alloying elements than currently available metastable β-titanium alloys.