Twin Structures Associated with Ordering in Evaporated Thin Films of Cu60Au40

Abstract

Electron diffraction and microscopic observations were made on twin structures associated with ordering in single crystalline films of Cu₅₀Au₄₀ prepared by vacuum evaporation. Crystallographic relationships of the twinned region in the ordered phase were determined with respect to the disordered cubic phase. The twin plane was parallel to {101} of the tetragonal CuAu I. It was usually found in slowly cooled specimens that the twin plane was normal to the film surface, and thus the c-axis of CuAu I in the twin lamellae was lying in the film plane making an angle of about 2° with the principal axis of the original cubic phase. The results are discussed in comparison with the observations of previous workers.