Abstract: Using Instron 1342 at a displacement rate of 0.5 mm/min, tensile tests were conducted in hotrolled and annealed commercial pure titanium at room temperature and 77 K, respectively. Fracture surfaces and microstructures after tests were investigated by SEM and TEM respectively. The results show that both the strength and the ductility of titanium at 77 K are higher than those at room temperature. The main deformation mode of pure titanium changes from slipping at room temperature to twinning at 77 K. Twinning induced plasticity is put forward to interpret the abnormal high ductility of titanium at low temperature of 77 K.

Key words: titanium; mechanical properties; twinning