Abstract:Three kinds of alloys were designed by making the niobium equivalent to eight approximately, compositions of alloys are Ti-45Al-8Nb-0.2B，Ti-45Al-7Nb-0.1Hf-0.1Y-0.2B，Ti-45Al-4Nb-0.5Hf-0.1Y-0.2B，(at.%). The interrupted oxidation behaviors of alloys at 900℃ in static air were studied. The results showed that combined addition of Hf and Y has been enhanced adherence between the oxide film and the substrate; Ti-45Al-4Nb-0.4Hf-0.1Y-0.2B alloy with the low Nb/Hf ratio has lower oxidation weighting and good oxidation resistance, Ti-45Al-7Nb-0.1Hf-0.1Y-0.2B alloy with the high Nb/Hf ratio has higher oxidation weighting and poor oxidation resistance. Oxidized samples were examined by scanning electron microscopy ( SEM ), energy dispersive x-ray analysis ( EDX ) and x-ray diffraction analysis( XRD), it was found that combined addition Hf and Y have been promoted the whisker growth formation of Al2O3 oxide scale, which improved adherence of the oxide film; a large number of continuous and compact Al2O3 oxide scale has found in the alloys with low Nb/Hf ratio, that has been improved oxidation resistance of alloy; in the alloy with high Nb/Hf ratio external oxidation resulted in higher oxidation weighting and poor oxidation resis-tance.