Abstract
In-situ microscopic video cinematography of the sample in a compression test machine and post-mortem 3-D atomic force microscopy (AFM) were used for the surface study of the order-disorder transformation on CuAu single- and polycrystalline samples. A special control of the compression force allowed to determine the thermal expansion of the sample in the compression axis.
The change of symmetry from the disordered fcc structure to the tetragonal CuAuI-phase or the orthorhombic long-period structure CuAuII is accompanied by the anisotropy of lattice parameters and also by local generation of c-variants of structural domains. Macroscopic results of these processes can be observed as a dynamic change of the surface morphology and external dimensions of the sample. These effects are connected with orientation of c-variants with respect to the surface of the sample (so called surface effect) and with respect to the compression axis (so called stress ordering effect).

Key words
copper-gold intermetallic compound, long-range order, order-disorder transformation

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