Martensitic Structure Evolution During Deformation and Its Correlation with Solution Temperature in Metastable Β Titanium Alloys

In this study, we explore the evolution of martensitic structures during deformation and their correlation with solution temperature in a metastable β-type Ti–10V–2Fe–3Al alloy. After a solution treatment at 760 °C, microstructures consist of equiaxed β grains and primary α particles. Increasing the solution temperature to 780 °C minimally affects equiaxed β grain size (~4.1–4.7 μm) but significantly reduces the α phase volume fraction. The α particles become scarce and completely absent following solution treatments at 800 and 820 °C, where the β grain size grows to ~109.1 and ~151.3 μm, respectively. Thermally-induced martensite (TIM) α″ laths are formed in specimens solution-treated at 770 °C or higher, predominantly populating the β grains of the specific specimens solution-treated at 800 and 820 °C. All solution-treated specimens exhibit a double yielding phenomenon. For specimens solution-treated at 760–780 °C, this results primarily from the stress-induced martensitic transformation (SIMT) process, while for those solution-treated at 800 and 820 °C, it mainly arises from the martensite reorientation (MR) process. The triggering stress for the SIMT/MR process increases with increasing solution temperature. In early deformation stages, TIM α″ laths initially undergo the MR process, transforming into a favored α″ variant, and the SIMT process can occur concurrently. As deformation progresses, the α″ phase changes orientation continuously through deformation twinning, transforming into the favored α″ variant dictated by the evolving stress conditions. This study provides insights into martensitic structure evolution and its influence on mechanical properties in metastable β titanium alloys.