To explore the effects of Cr2O3 on the nucleation of alpha-Al2O3 and the nucleation interface of alpha-Al2O3/Cr2O3, the oxidation of Al45Cr7 powder at 650-720 degrees C for 9-500 h in air was carried out in this paper. The morphologies and structures of oxidized powder were investigated by XRD, SEM and TEM. The results showed that Cr2O3 formed at the outset of the oxidation, and acted as the nucleus of alpha-Al2O3 immediately. Then the oxidation of Al at the interface of Cr2O3/Al45Cr7 occurred, resulting the direct nucleation of alpha-Al2O3 on (0 0 1) facet of Cr2O3. The interface of alpha-Al2O3/Cr2O3 was found to be (0 0 1)alpha-Al2O3/(0 0 1) Cr2O3, with an angle about 5 degree between them. Besides, the effects of temperature on the nucleation of alpha-Al2O3 were also studied. (C) 2012 Elsevier B. V. All rights reserved.