The recrystallization and thermal oxidation behavior of CP-titanium

In this study, the effect of cold working on the recrystallization and thermal oxidation behaviours of Grade 2 quality commercial purity titanium (CP-Ti) were examined. Recrystallization tests were carried out on the 23%, 35% and 50% cold worked samples at various temperatures in between 550 and 700 °C. Thermal oxidation of the cold worked samples was conducted at 600 and 650 °C. Recrystallization activation energy was calculated as 66-88 kJ/mol. Since thermal oxidation progresses by oxide layer growth and diffusion of oxygen into the substrate (oxygen diffusion zone formation), oxygen diffusion zone formation activation energies of 149-170 kJ/mol were calculated for the examined cold work ratios. These results indicate that when a cold worked CP-Ti was subjected to thermal oxidation treatment to improve its surface hardness and wear resistance, it loses its bulk hardness due to recrystallization.