Reactivity of a Ti–45.9Al–8Nb alloy in air at 700–900°C

Abstract

A Ti–45.9Al–8Nb (at%) alloy with a lamellar structure (γ+α2) was oxidised in air at 700, 800, 850 and 900°C in isothermal and thermal cycling conditions. The reaction progress was followed by thermogravimetric measurements. In isothermal conditions the oxidation kinetics followed approximately a parabolic rate law and the rate constants ranged from about 10–12 kg2 m–4 s–1 at 700°C to 10–10 kg2 m–4 s–1 at 900°C. The oxide scales were built of Al2O3 and TiO2, the former being the main component of the outermost layer. The oxidation behaviour of Ti–45.9Al–8Nb was referred to a commercial titanium alloy, WT4 (Ti–6Al–1Mn), and selected oxidation-resistant alloys.