Research on flow stress behavior, constitutive modeling, processing mapping and microstructure evolution of as-cast Ti-6Mo-4Al-4Zr-3Nb-2Cr-1Fe alloy during hot deformation in (α plus β) region

To investigate the hot deformation behavior and the microstructure evolution of Ti644321 alloy in alpha+(3 region, the hot compression tests were conducted within the temperature range from 720 to 810 degrees C and strain rate from 0.001 to 1 s-1. The as-cast Ti alloy mainly consists of coarse equiaxed (3 phases. During the thermal deformation of alloys in the (alpha+(3) region, lots of alpha phase precipitates. At lower strain rates, the microstructure consists of fine spherical or short rod-shaped alpha phase embedded within the (3 matrix. This indicates that under thermal deformation conditions, the alpha phase undergoes spheroidization, which is caused by the wedging of (3 phase. At high strain rates, dynamic recrystallization is difficult to occur due to insufficient time consumption or sustained generation of dislocations. With the increase of deformation temperature, the number of primary alpha phases decreases, and the size also slightly increases. The relationship between microstructural characteristics and power dissipation efficiency (eta) is established through the analysis of the hot processing map and corroborated by microstructural observations. Flow localizations and lamellar kinking of alpha phase appear in the instability region. The optimal processing parameters for Ti644321 alloy are in the medium temperature (740-770 degrees C) and the low strain rate (0.001-0.03 s-1). The dynamic recovery of (3 phase and the spheroidization of alpha phase are the main softening mechanisms in this area.