Antiphase Domains in Ordered Au3Cu Alloys

Alloys having compositions from 42%−9% Cu in the Cu‐Au system were investigated to determine the nature of the antiphase structures and the range of the ordered Au3Cu structure in this region. The single‐crystal thin‐film technique was used to prepare the specimens and the structure was determined by electron diffraction. The ordered Au3Cu I structure exists as an equilibrium phase from 38.5%−9% Cu. Unlike the Cu3Au and CuAu alloys, however, periodic antiphase structures are not observed as an equilibrium phase in these alloys. Increasing the electron‐atom ratio by the addition of a third element, for example, Al, results in the formation of a periodic antiphase structures as predicted. It is shown that the low ordering temperature is responsible for the failure of a periodic antiphase structure to appear in these alloys.