Deformation Characteristics and Microstructure Evolution of Ti-6Al-4V Alloy with 0.31 wt.% Hydrogen

The isothermal constant strain rate compression test of Ti-6Al-4V alloy with a hydrogen content of 0.31 wt.% was carried out on a Gleeble-1500 thermomechanical simulator. The thermal deformation behavior at temperatures of 700-950 degrees C and strain rates of 0.001-10 s(-1) was studied. The results show that the flow stress of the alloy is sensitive to the deformation temperature and strain rate. The flow stress decreases with increasing deformation temperature and increases with increasing strain rate. Using the Arrhenius hyperbolic sine function, the constitutive equations for the Ti-6Al-4V alloy with 0.31 wt.% hydrogen in the alpha + beta two-phasic region as well as in the beta single-phase region were derived. Processing maps were established by superimposing the instability map and the power dissipation map. Compared with the Ti-6Al-4V alloy without hydrogen, the flow stress of the alloy is reduced, and the microstructure becomes refined. The beta grain size increases with increasing deformation temperature. The dynamic recrystallization rate decreases with decreasing strain rate. The instability phenomena often occur at low temperatures. The instability region grows steadily with increasing strain. The alloy should be avoided in thermal processing at high strain rates (> 0.01 s(-1)) and low temperatures (< 800 degrees C).