In this study, the high-temperature microstructural characteristics of the Ti-5Al-1Sn-1Fe-1Cr (Ti-5111) alloy were determined by optical microscopy, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry. During solution treatment between 800 and 1000 °C, the phase transformation sequence of the alloy was found to be (α + β) → (α + α′ + β) → (α + α′ + α″ + residual β) → (α′ + β). The residual β phase subsequently transforms to the α″ phase during quenching. The driving force for this transformation is the cooling rate. The martensite starting point (Ms) and β transus temperature of the Ti-5111 alloy are nearly 860 and 960 °C, respectively. These values are lower than those of the Ti-6Al-4V alloy. Moreover, it is believed that the concentration of Al in α′ martensite plays a crucial role in the formation of the twin-type martensite.
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