Neutron scattering study of short-range clustering in CuNi(Fe) alloys

The thermodynamic equilibrium state of short-range clustering and the kinetics of short-range clustering are studied for two CuNi(Fe) alloys by means of neutron scattering. The first four Warren-Cowley short-range order parameters are determined for different equilibrium states of a Ni-32 at.% Cu alloy between 648 and 973K. The coherent spinodal temperature Tc,s is determined for a Ni-32 at.% Cu alloy (Tc, s=(500+or-25)K) and for a Ni-30 at.% Cu-5 at.% Fe alloy (Tc,s=(675+or-24)K). It is shown that for the compositions investigated the conventional linearised theory is valued for the relaxation of short-range clustering only for those cases where the degrees of clustering in the initial and final states do not differ too much. A procedure proposed recently for the dynamical scaling of the structure function during spinodal decomposition is also tested for the structure functions measured during the short-range clustering process. It is found that the procedure does not provide useful results for the dynamics of short-range clustering.