Phase-field simulation of diffusion couples in the Ni-Al system

By linking thermodynamic and atomic mobility databases with two-dimensional phase-field simulation, the evolution of interdiffusion microstructures in a series of Ni-Al diffusion couples associated with the gamma, gamma', and beta-phases was studied. The formation and subsequent growth of the gamma'-phase layer in beta/gamma and gamma' + beta/gamma diffusion couples reproduced the experimental observations well. Moreover, the effect of coherent strain on the gamma-gamma' microstructural evolution, as well as that of an external compressive force on the gamma + gamma'/gamma + gamma' diffusion couple, was investigated. The phase-field simulated concentration profiles of some of the Ni-Al diffusion couples were also compared with the corresponding experimental data and the results of one-dimensional DICTRA (Diffusion Controlled TRAnsformations) simulations. A discussion of the rafting direction was also made by comprehensively comparing the phase-field simulations with the predicted results from an elastic model.