Dynamic stress/strain partitioning of distinct early plastic deformation behaviors in ω-enhanced TRIP/TWIP titanium alloys

The ω-nanoprecipitates demonstrate high compatibility with transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) effects, establishing ω-enhanced TRIP/TWIP titanium alloys as a promising strategy to overcome the strength-ductility trade-off. However, both ω-induced localized dislocation activity and stress-induced martensite (SIM) pose potential risks of premature plastic instability. To rigorously interpret the origination of distinct early plasticity behaviors, the comprehensive compositions screening methodology, combining Density Functional Theory, Cluster Expansion, Monte Carlo and Ab Initio Molecular Dynamics, was performed to focus on β phase stability, β-ω continuous slip barriers, and solid-solution/precipitation strengthening effects. Selected Ti-9.33Mo-12.42Zr and Ti-9.18Mo-15.71Zr alloys (wt.%) exhibit nearly overlapping engineering stress-strain (σ_e-ε_e) curves after identical thermomechanical processing, yet demonstrate Lüders-type strain and uniform deformation respectively. The two early plasticity behaviors under comparable yield stresses were deeply analyzed for the first time. Our results indicate that ∼20 % ε_e Lüders plateau was attributed to deficient work-hardening caused by the ineffectiveness of SIM-mediated dynamic Hall-Petch (DHP) effect, wherein ω-induced localized dislocation plasticity and SIM jointly carried deformation. Moreover, early uniform deformation could be stabilized by {332}〈113〉_β deformation twins (332DT) through the pinning on intergranular deformation and DHP effect-driven work-hardening. Furthermore, local stress concentrations relaxation and strain accommodation of 332DT intersections were achieved via triple-mechanism synergy: twinning splitting, dislocation activation, and secondary twinning. Ultimately, regulation routes and controversies surrounding ω-enhanced TRIP/TWIP titanium alloys have been systematically reevaluated. Our theoretical and experimental results provide actionable insights for the development of new titanium alloys.