MULTICOMPONENT DIFFUSION - IMPLEMENTATION OF THE SQUARE-ROOT DIFFUSIVITY METHOD VIA THE PROFILER COMPUTER-PROGRAM

We evaluate the square-root diffusivity method as implemented in a new computer program Profiler developed by Brockman and Morral in 1993 to model interdiffusion of components in multicomponent alloys, a proces s which is of great importance in the materials sciences. Two multicom ponent alloys joined along a planar interface form a classical one-dim ensional diffusion couple in which the flux of any given component is affected by the flux of the others. A special relationship exists betw een the spatial extent of penetration of the various diffusing species and the square root of time, from which the usefulness of the square root of the diffusivity matrix becomes evident. Profiler, written in T urbo Pascal for use on personal computers, calculates the variation, w ith time and distance, of the concentrations of the n species diffusin g across the interface of the single-phase diffusion couple using the square-root diffusivity method. Diffusion profiles calculated by Profi ler are compared to the published experimental data of Thompson et al in 1990 and Dayananda and Kim in 1979. Profiler is also used to invest igate diffusion paths as a function of ternary alloy concentration in Cu-Ni-Zn couples. We conclude that Profiler accurately predicts the fo rm of the two independent diffusion fields (e,g. predicting the existe nce or absence of extrema in the penetration curves). The slopes of th e diffusion profiles and the precise location of compositional extrema are, however, shown to be dependent upon the accuracy of the alloy th ermodynamic data selected by the user. Profiler is especially useful a s a survey tool for estimating the potential occurrence and magnitude of compositional extrema and other peculiarities of multicomponent dif fusion. in addition, the interpretation of diffusion penetration data obtained from electron microprobe analysis can be enhanced by prior kn owledge that compositional extrema may occur within multicomponent dif fusion zones.