The Oxidation Behavior of Several Ti-Al Alloys at 900°C in Air

Ti-23Al, Ti-50Al and Ti-50Al-2Nb (at.%) wereoxidized in air at 900°C for times up to 1130 hr.The resulting oxide scale structures were analyzed ingreat detail by metallographic and microprobe investigations and theAl2O3 structures in the complexoxide scales were correlated with the course of thethermogravimetric curves. It appears that in order toachieve long-term protective behavior of the scales, it is necessary to stimulate theformation of a thin Al2O3 barrierat the scale-metal interface and not at a position inthe outer part of the scale. The Nb effect seems to bemostly due to this stimulation of anAl2O3 layer at theinterface.