Anomalous small-angle x-ray scattering determination of the partial structure factors and kinetic study of unmixed Cu-Ni-Fe alloys

Abstract

Different unmixed states of a Cu-Ni-Fe alloy have been studied by anomalous small-angle x-ray scattering (ASAXS). The data were obtained at different x-ray energies near the Fe and Ni absorption edges: ASAXS intensities increase by a factor of 3, varying with the atomic contrast (with respect to Cu). Various methods for the determination of partial structure factors (PSF) have been tested and results are found reliable if we use the intensity data in the proximity of at least two edges. The homoatomic PSF curves have similar shapes with a maximum $I_m$ which increases and shifts towards lower q values as the power laws $I_m$∼$t^{0.80}$ and $q_m$∼$t^{\mathrm{-}0.26}$, and the scaling behavior is obeyed. These features are very similar to the ones observed during late stages of aging of concentrated binary systems. On the other hand, there is evidence that the phase separation of Cu-Ni-${\mathrm{Fe}}_{0.15}$ at 500?deC cannot be modeled by a two-phase system, and different possible partitioning of Cu, Ni, and Fe are discussed.