Achieving high work-hardening and high plasticity of metastable β-Ti-xV-5Zr–3Al–2Cr alloy through α" martensite

Metastable β titanium alloys have garnered significant attention owing to their excellent work-hardening ability and plasticity. In this work, four titanium alloys with varying initial structures were obtained by adjusting the V content: Ti-xV-5Zr–3Al–2Cr (x = 9,12,13,15 wt.%) (TxV). The influence of stress-induced α" martensite transformation (SIMα") on the mechanical properties of alloys was systematically investigated. The T9V alloy, despite its high content of α′ martensite, showed a total elongation of 27.7 %, attributed to SIMα" alleviating stress concentration. In the T12V and T13V alloys, SIMα" initially occurred, followed by the formation of {332} <113> twins within α" martensite, which enhanced the uniform deformation ability, resulting in total elongation reached 44.7 % and 50.1 %, respectively. Concurrently, the reduction in the mean free path of dislocations and the reorientation of α" martensite improved work-hardening ability. Notably, the existence of kind bands endowed the T12V alloy with a superior work-hardening rate (14.1 GPa). In contrast, the T15V alloy, which lacked SIMα" during deformation, resulting in a lower total elongation of 19.0 %.