Influence of hydrogen on hot deformation behavior and microstructure of pure titanium

The influence of hydrogen on the hot deformation behavior and the microstructure after deformation of pure titanium crystal was investigated. The results show that hydrogen in pure titanium crystal can reduce the flow stress of hot deformation; The flow stress peak is decreased best by 60% in a Ti-H crystal specimen deformed at 600–800 °C and the peak flow stresses exhibit a trough behavior with the hydrogen concentration, that is, there is a minimum of peak flow stress at a certain hydrogen concentration. Through the analysis of microstructure, the great amounts of needle-like martensite and the small number of dislocations within the sub-grains in Ti-H crystal after hot deformation. These indicate that the hydrogen can increase the volume of β phase and can promote the dynamic recovery in the deformation process at high temperature, as a result, it decreases the flow stresses effectively.