Oxidation of Ti–6Al–4V alloy between 450 and 600°C. Evolution of microstructure and mechanical properties

Titanium alloys are widely used in many applications thanks to their good corrosion resistance and to their high specific modulus. However, at temperatures above 450°C, oxidation must be taken into account to improve life assessment of components. Especially for long-term exposures, oxidation leads to an oxide scale along with an oxygen enrichment in the metal below this oxide scale. In this study, the oxidation behaviour of Ti– 6Al–4V is investigated between 450 and 600°C for a maximum duration of about 6800 h. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) are used to characterize the oxide layer and the layer affected by oxygen uptake. The local oxygen content is quantified. Vibration tests are performed to determine elastic properties on thin specimens with different thicknesses affected by oxygen enrichment. Creep tests are also carried out to quantify the influence of this oxygen uptake on viscoplastic behaviour. An oxygen-enriched zone occupying 5% of the cross-section of a specimen is sufficient to induce detectable changes in its creep behaviour