Diffusion Limited Interface Kinetics in Multicomponent Systems

Abstract

ABSTRACTThe stability of phases in materials can be related to reactions occurring at their interfaces, for example fiber/matrix reactions in composites. The reaction can be modelled in a simple way, even for multicomponent systems, when it is diffusion controlled and when no intermediate phases form. In the current work a model is proposed that assumes local equilibrium at the interface and small concentration differences in each phase. The physical properties required for the model are the “square root diffusivity” for each phase and the applicable phase diagram. The model is applied to predicting concentration profiles and interface velocities for the reaction of a B2 aluminide containing Ni-34at%Cr-12at%Al with various Ni-rich, gamma solid solutions containing Cr and Al. The example shows how varying the gamma composition can alter the aluminide stability with respect to dissolution or growth. In addition, a simplified form of the model is given for extrapolating experimental interface velocity data.