An ω phase in the Cu-16.5 at. pct Sn alloy

In many zirconium- and titanium-base alloys a precipitate of an ω phase is found after quenching from the high temperature β phase region. In a Cu-16.5 at. pct Sn alloy the same phase is present after quenching from the γ-phase region to room temperature. The quenched Cu-Sn alloy shows electron diffraction effects which are very similar to those of the zirconium- and titanium-base alloys, i.e., diffuse scattering and shift of the ω reflexions. In order to explain this shift a model, based on the presence of certain faults in the ω structure, is presented. After aging at 100° and 130°C the ω phase is replaced by a phase which closely resembles the stable Cu-Sn σ phase. Nuclei of this phase are thought to be at least partially responsible for the diffuse scattering observed.