In this study, the flow behavior and α phase morphology evolution of Ti-6Al-4V dual-phase alloy with an initial martensitic microstructure were investigated under non-isothermal deformation. The initial process temperature and cooling rate were approximately 935 °C and 1 °C/s, respectively. Non-isothermal deformation was performed to examine the effects of strain (0.4, 0.7, and 1.2) and strain rate (0.01 −1, 0.1 −1, and 1 −1) on the α phase morphology. The results indicated that at high strain rates (0.1 −1 and 1 −1), the flow curves exhibited work softening after the peak stress without reaching a steady-state condition, due to limited diffusion time. At a low strain rate of 0.01 s−1, a slight work softening was followed by a minor increase in flow stress, attributed to the β → α phase transformation, and eventually a steady state was achieved due to a dynamic balance between work hardening and work softening. With increasing strain and decreasing strain rate, the thickness and globularization of the α lamellae increased, resulting from sufficient diffusion time for β → α phase transformation and the availability of more nucleation sites. Kinking and splitting of the α lamellae were identified as the primary mechanisms of work softening at high strain rates, whereas at low strain rates, work softening was dominated by phase transformation and globularization. Microstructural observations confirmed that non-isothermal deformation promoted β → α phase transformation, leading to higher hardness in the deformed samples compared to the non-deformed ones.

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