Phase dependent restoration mechanisms of TC8 titanium alloy during hot compression in the two phase region

The TC8 titanium alloy was isothermally compressed at 1133 K and 1213 K in the (α+β) two phase region. The microstructural evolution and restoration mechanism in the α and β phases were characterized by optical microscopy and transmission electron microscopy. The results show a significant effect of phase content on the microstructural evolution and restoration mechanism. The grain refinement occurs in the α phase at both temperatures, but in the β phase only at the higher temperature of 1213 K. This difference in microstructural evolution is attributed to the different temperature dependence of restoration mechanisms in the two phases. A significant increase in the volume fraction of β phase makes the restoration mechanism in the β phase change from dynamic recovery (DRV) to dynamic recrystallization (DRX), which subsequently induces the β grain refinement.