Short-term oxidation behaviour of Ti-Al6-V4 alloy in air at temperatures in range 600-700 degrees C

The findings of a study on the oxidation behaviour of a commercially pure Ti-Al6-V4 alloy in air between 600 and 700 degrees C are reported, based on the determination of the kinetic curves, oxygen profiles in the metal beneath the scale, and the examination of the morphology and composition of the scales. The oxidation kinetics at short time intervals (up to 300 hours) were consistent with a parabolic model at 610 and 655 degrees C. Differently, at 700 degrees C, an initial parabolic oxidation was followed by an approximately linear rate after nearly 100 hours of oxidation. From measurements of oxygen penetration diffusion constants and the corresponding activation energies were estimated for oxygen diffusion in the alpha-phase. The scaling behaviour was observed to depend on the oxidation temperature. At 610 degrees C the scale appeared composed of just one very thin and adherent layer. However, at the higher temperatures, a lamellar structure began to develop, best evidenced by exfoliation of part of the scale. Finally, X-ray microanalysis across the scales confirmed the trend of the aluminum to pile up near the external interface of each layer, as reported by a number of research workers.