Flow Softening and Microstructural Evolution of Near Β Titanium Alloy Ti-55531 During Hot Compression Deformation in the Α+Β Region

In order to investigate the microstructural evolution and dynamic softening mechanisms of Ti-55531 alloy during hot compression in the α + β phase region, hot compression tests were performed at temperatures of 760–840 °C and strain rates of 0.001–1 s−1, and the microstructure of the material under each deformation condition was analyzed by scanning electron microscope and electron backscatter diffraction techniques. The results show that the flow softening phenomenon is influenced by a combination of mechanisms. The deformation heat causes significant flow softening of the material at a strain rate of 1 s−1, while dynamic recrystallization contributes little to flow softening. Due to the shift in αp phase volume fraction, the flow softening fraction f∆Vα reduces as deformation temperature and strain rate increase, from 16.6% at 760 °C and 0.001 s−1 to 1.4% at 840 °C and 1 s−1. The flow softening fraction fΔσSF is 3.95% at 790 °C and 5.34% at 820 °C as a result of the texture evolution.