THE DIFFUSE-SCATTERING METHOD FOR INVESTIGATING LOCALLY ORDERED BINARY SOLID-SOLUTIONS

Diffuse-scattering investigations comprise a series of maturing methods for detailed characterization of the local-order structure and atomic displacements of binary alloy systems. The distribution of coherent diffuse scattering is determined by the local atomic ordering, and analytical techniques are available for extracting the relevant structural information. An extension of such structural investigations, for locally ordered alloys at equilibrium, allows one to obtain pairwise interaction energies. Having experimental pairwise interaction energies for the various coordination shells offers one the potential for more realistic kinetic Ising modeling of alloy systems as they relax toward equilibrium. Although the modeling of atomic displacements in conjunction with more conventional studies of chemical ordering is in its infancy, the method appears to offer considerable promise for revealing additional information about the strain fields in locally ordered and clustered alloys. The diffuse-scattering methods for structural characterization and for the recovery of interaction energies are reviewed, and some preliminary results are used to demonstrate the potential of the kinetic Ising modeling technique to follow the evolution of ordering or phase separation in an alloy system.