Observation on the Interface of α-Al2O3/Cr2O3: Prepared by oxidation of Al45Cr7

To explore the effects of Cr2O3 on the nucleation of α-Al2O3 and the nucleation interface of α-Al2O3/Cr2O3, the oxidation of Al45Cr7 powder at 650–720 °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 α-Al2O3 immediately. Then the oxidation of Al at the interface of Cr2O3/Al45Cr7 occurred, resulting the direct nucleation of α-Al2O3 on (0 0 1) facet of Cr2O3. The interface of α-Al2O3/Cr2O3 was found to be (0 0 1)α-Al2O3/(0 0 1)Cr2O3, with an angle about 5 degree between them. Besides, the effects of temperature on the nucleation of α-Al2O3 were also studied.