Abnormal work hardening in a TRIP-assisted metastable β titanium alloy under high strain rate loading

Abstract

In this study, the dynamic tensile deformation behavior and microstructural evolution of a metastable β titanium alloy (Ti–10 V–2Fe–3Al, Ti-1023) with a single β phase structure were investigated at ambient temperature and high strain rates ranging from 1000 s−1 to 4000 s−1 on a split Hopkinson tension bar (SHTB) system. The dynamic tensile properties and work hardening ability exhibited a significant strain rate dependence. The calculated strain rate sensitivity (0.026–0.090) showed a strong strain and strain rate hardening ability. Microstructural analyses indicated that the dynamic deformation mechanisms were dislocation slip and deformation-induced α" martensite at all strain rates, while deformation-induced ω phase was activated beyond a strain rate of 2000 s−1. Deformation-induced phase transformations during dynamic tensile deformation led to a significant transformation-induced plasticity (TRIP) effect and a double-yielding phenomenon. As strain rate increased, deformation-induced martensitic transformation and the corresponding TRIP effect were suppressed, while work hardening rate first increased and then rapidly decreased. This abnormal TRIP effect on work hardening behavior was mainly due to the deformation-induced ω phase, promoting the dislocation plasticity in the β matrix and contributing to extra work hardening ability.