High-Temperature Oxidation Kinetics and Behavior of Ti-6Al-4V Alloy

Owing to the high-temperature reactivity of titanium, the oxidation and alloying of titanium during hot working processes is an important variable. The oxidation behavior of Ti-6Al-4V alloy in air was investigated at various temperatures between 850 and 1100 degrees C for different times. The oxidation kinetics were determined by isothermal oxidation weight gain experiments. The results showed that the oxidation kinetics approximately obeyed a parabolic law. The activation energy of oxidation was estimated to be 199 and 281 kJ mol(-1) when temperature was above and below the beta transformation temperature (T (beta)), respectively. A model to predict oxidation extent was established based on experimental observations. The oxide scales mainly consisted of TiO2 with a small amount of Al2O3 and TiVO4. The alpha case was defined as solid solution formed because of oxygen diffusion into the substrate. The difference in the morphology and the formation mechanism of the alpha case at different temperature ranges was mainly owing to the participation of the grain boundary and grain orientation of the nucleation site.