Parameterization of Diffusion Characteristics of Atomic-Order Relaxation Kinetics in Ni–Al Alloys

To study diffusion characteristics in substitutional f.c.c.-Ni–Al alloys, we review, analyse, and use the kinetic models, in which the relaxation of correlation parameters for the atomic distribution causes the time dependence of both the diffuse-scattering intensity I and the residual electrical resistivity ρ. Using the parameterization of the available literature data about the measurement of the residual electrical resistivity during the isothermal annealing of alloys, the most characteristic relaxation times of ρ after quenching of the alloys and its equilibrium value ρ∞ are estimated. The maximum characteristic relaxation time of the atomic order of such alloys is determined, and the curves of the time dependence of the normalized change in intensity ΔI are predicted based on the hypothesis of the coincidence of the largest characteristic relaxation times for I and ρ. The relaxation process is accompanied by both the increase in the number of clusters with the presence of short-range order in their structure and the degree of their order that is consistent with both the results of computer modelling of local atomic ordering using the Monte Carlo method and the model of inhomogeneous short-range order.