A Study on Alpha-Case Depth in Ti-6Al-2Sn-4Zr-2Mo

Isothermal oxidation experiments in air were performed on Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) with a bimodal microstructure in the temperature range 811 K to 922 K (538 A degrees C to 649 A degrees C) for up to 500 hours, and alpha-case depths were quantified using metallography. Alpha-case depth followed a parabolic variation with time. Alpha-case depths in excess of 10 mu m formed above 811 K (538 A degrees C) and 100-hour exposures. An activation energy of 244 kJ/mol was estimated for diffusion of oxygen in the alpha phase of Ti-6242.