The kinetics of ordering and coarsening in single-crystal ${\mathrm{Cu}}_3$Au are studied by use of time-resolved x-ray scattering. After a quenching from high temperatures to fixed temperatures below the order-disorder temperature, three regimes are apparent: nucleation, ordering, and coarsening. The superlattice peaks are anisotropic, reflecting the domain structure. The line shape of the scattering function changes with time during the crossover from the ordering to the coarsening regime. The late-stage coarsening is consistent with curvature-driven growth.

• Received 10 March 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.718