Investigation of the interface structure of Cu/oxide precipitates in an internally oxidized Cu-Al alloy

θ-Al₂O₃, α-Al₂O₃ and CuAlO₂ precipitates were found in an internally oxidized Cu-2.6wt.% Al alloy. The orientation relationships between these oxides and the matrix Cu were determined from the selected area diffraction technique. The θ-Al₂O₃ has a monoclinic structure and the orientation relationship between the matrix Cu and θ-Al₂O₃ was determined to be [211]Cu//[13̄2]θ{symbol} and (113)Cu//(201̄)θ{symbol}. The CuAlO₂ is a hexagonal crystal structure. The orientation relationship between Cu and CuAlO₂ was determined to be [110]Cu//[11̄00]CuAlO₂ and (113)Cu// (0001)CuAlO₂. The interphase boundary plane between matrix Cu and both oxides are near (113)Cu. An α-Al₂O₃ oxide observed within a CuAlO₂ precipitate had the orientation relationships [11̄00]CuAlO₂//[2110]α and (0001)CuAlO₂//(0001)α. The high resolution imaging technique was applied to study the atomic structure of a Cu/CuAlO₂ interface. The image simulation suggests that the terminated plane of CuAlO₂ in the interphase boundary is an oxygen plane. The Cu atoms in (113)Cu are all in 'lock-in' position in the interface.