Effects of solution temperature on microstructure and property of Ti55531 alloy

Effects of different solution temperature on microstructure and mechanical properties of Ti55531 titanium alloy were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindentation methods.It is found that the microstructure of the as-forged alloy consists of the globular α phases and β phases. After solution treating at 780℃ and 840℃, and then aging at 540℃ for 1 h, the microstructure of the alloy is composed of primary α phases, secondary α phase and β phase, and the secondary α phase yields the orientation relationship of (1101) α//(110) β with β phase. With the solution temperature increasing, the volume fraction of the globular primary α phase reduces drastically, while the volume fraction of the secondary α phase increases. The hardness of secondary acicular α phase is much higher than that of the primary α phase and β phase, resulting in the hardness of the alloy soluted at 780℃ and 840℃ increase by 8.5% and 10.3% in comparison with the as-forged alloy, respectively.