Neutron scattering study on decomposition in Cu-Ni-Fe alloys

The validity of current theories for describing decomposition was investigated for a number of Cu-Ni-Fe alloys by means of neutron scattering. The dynamical scaling procedure of the structure function during decomposition was successful only in some particular cases of decomposition. As a measure for the size of the nuclei that are formed during decomposition of an alloy, we considered the radius of gyration and the first and second moment of the scattering function. The coarsening of the alloys could, except for the later stages, be described by the Lifshitz-Slyozov theory. Superlattice reflections were found in the diffraction pattern of ${\mathrm{Cu}}_{52}$ ${\mathrm{Ni}}_{38}$ ${\mathrm{Fe}}_{10}$ after annealing for 665 and 857 h at 733 K. We attribute this to the formation of an ordered ${\mathrm{Ni}}_3$Fe-type structure.