The Structure of a Low Energy Interface in Ag-Ni

Using the sphere rotation method, low energy orientations of Ag-Ni boundaries have been determined by sintering Ag spheres on a (011)Ni-plate [1]. The pole figures reveal that approximately 70% of all spheres have rotated into the orientation (011)Ag [01]Ag ∥ (011)Ni [01Ni. In the following, this orientation is called “parallel cube” (PC)-because all equally indexed directions and planes are parallel. This orientation was also observed in earlier epitaxy investigations [2]. In addition, results from sphere rotation experiments on other fcc materials (Au/LiF, Au/KCl, Au/NaCl, Ag/NaCl, Au/MgO, and Cu/MgO [3,4]) likewise show that the PC orientation is by far the most intensely populated and must be assumed to have particularly low energy. From these observations the question arises: why is the PC orientation energetically favoured in so many systems, despite widely varying misfit and bonding character? As a representative system with large misfit (approx. 15%), heterophase boundaries in the system Ag-Ni are being examined by TEM. An important aspect is the possible existence of misfit dislocations whose expected arrangement can be calculated by the O-lattice theory if they are assumed comparable with bulk edge dislocations. The expected misfit dislocations are located midway between the O-lattice points (Fig. 1). For the compensation of the misfit in the PC orientation, two different dislocation types are necessary: