Study of Ti–6Al–4V alloy spectral emissivity characteristics during thermal oxidation process.

The infrared normal spectral emissivity of an oxidized Ti–6Al–4V alloy has been measured during a thermal oxidation process. It gradually increased with oxidation time below 873 K, and strong oscillation was observed above 923 K. To explore the possible reasons for emissivity variation under different temperatures and oxidation time, the changes of surface composition and roughness were investigated before and after oxidation by X-ray diffraction (XRD) and roughness tester. The surface oxide film thickness has been estimated by using the theory of radiative effects of films and the actual value of thickness has been measured utilizing spectroscopic ellipsometry (SE) and scanning electron microscopy (SEM), respectively. The measurement results were in good agreement with the estimated values. It is found that the interference effect of oxide film could be responsible for the oscillatory behavior in spectral emissivity. The thickness values indicate that the oxide film growth follows parabolic law and that the growth rate increases rapidly above 923 K. [ABSTRACT FROM AUTHOR]