Electron-microscopic study on the low-temperature phase of the Co-rich CoV alloy system

An electron-microscopic study on a 15.6 at% V—Co single crystal annealed at 600 °C for 168 h is carried out to determine the crystal structure of the low-temperature f.c.c. phase in the Co-rich CoV alloy system. From the diffraction patterns observed in various crystallographic orientations, it is found that this phase is of the Cu3Au-type superlattice structure. The dark-field images formed with the superlattice reflections reveal that these extra reflections originate not from any special regions of the specimen, but from its whole area. Superdislocations and antiphase boundaries which are characteristic of the imperfections in the ordered alloy are also observed.