Cyclic deformation behaviour of commercially pure titanium at cryogenic temperature

Push-pull low-cycle fatigue tests were carried out on annealed and hot-rolled commercially pure titanium under total strain control at 77 K. Very obvious cyclic-hardening behaviour was observed at the beginning of fatigue for the strain amplitudes employed. A large number of twins with various appearances was observed in the microstructure of fatigued specimens of annealed and hot-rolled titanium. Three twinning systems, (112̄1̄), (11̄02) and (12̄12) types, are operative in the cyclic deformation of titanium. Twinning is considered to be the main deformation mode of pure titanium fatigued at 77 K and to be the main reason for the cyclic hardening of pure titanium at low temperature.