Microstructure evolution of Ti-6Al-4V with periodic thermal parameters during axial closed die rolling process

Highlights: • Gradient/periodic distribution is ubiquitous throughout the process. • The strain distribution in the center axis is linear. • The spheroidization efficiency of lamella α is enhanced. Due to the cooperation of the torsion, tension and compression in metal plastic flow process of axial closed die rolling (ACDR), the effect of deformation schedule on grain refinement is still ambiguous. Therefore, the evolutionary mechanism of microstructure with periodic thermal parameters during ACDR process was established through the numerical simulation and metallography experiment. The results show that gradient distribution is ubiquitous in most areas in terms of both the strain and temperature throughout the deformation process, except the strain distribution in the center axis. With regard to the microstructure, the spheroidization efficiency of lamella α phase is enhanced during the especial deformation schedule. Factors influencing the uniformity of the globular α phase size are based on the vibration frequency of periodicity thermal parameters. The efficiency of broken α_GB and the occurrence of DRX β have a closely related to the additional torsion.