DEFORMATION RESISTANCE AND RECRYSTALLIZATION OF COMMERCIALLY PURE TITANIUM IN THE HIGH-STRAIN-RATE HOT DEFORMATION.

The deformation resistance and recrystallization behavior in high-temperature working (600-850 degree C) with high strain rates (2-150 l/s), which covers most hot rolling conditions, have been investigated. Under the usual hot rolling condition, dynamic recrystallization does not occur and the resistance to hot deformation is determined by the balance between strain hardening and dynamic recovery. Flow stress sharply increases with increases in the impurity content at higher purity conditions, while the hardening rate due to the increase in the impurity content becomes smaller if the range exceeds a certain value. The recrystallization ad grain growth behavior of commercially pure titanium is similar to that of plain carbon steels in the austenite phase. In commercially pure titanium, deformation bands, which act as nucleation sites for recrystallization, are more easily formed than in plain carbon steels. The activation energy for hot deformation and recrystallization lies in a range between 220-260 kJ/mol.