Published online by Cambridge University Press: 28 February 2011
Particles of a cubic A12O3 phase in an internally oxidized CuAl alloy were imaged by HREM. These particles are triangular platelets which lie on {111} planes of the copper matrix and have a diameter of about 100nm. They grow by migration of ledges. The platelets are always twinned parallel to their triangular base. At the A12O3 /Cu interface, the lattice of the A12O3 lies either parallel or in twin orientation relationship to the fcc Cu lattice. The interface is always parallel to {111} planes of the A12O3. The lattice parameter of the A12O3 is 10% larger than twice the lattice parameter of Cu. However, HREM micrographs and weak beam micrographs of the A12O3 /Cu interface do not show localized misfit dislocations. HREM image simulations of model structures yielded evidence that the A12O3 particles have a highly disordered spinel type structure. The simulations also indicate that a partly occupied layer of oxygen atoms terminates the A12O3 at the interface with Cu.