Interdiffusion in the Al–Cu System

Abstract

Interdiffusion in the aluminum-copper system was investigated in the temperature range of 400° to 535°C with diffusion couples of pure aluminum and copper metals.In the aluminum-copper equilibrium phase diagram there are five intermediate phases in this temperature range, namely γ2, δ, ζ2, η2 and θ. Electron probe micro line analysis of specimens studied indicated that all of these phases were located in the diffusion layer.It appears that the layer growth of each phase is controlled by the process of volume diffusion since the rate of layer growth obeys the parabolic law. From the temperature dependency of the rate constants of layer growth, the activation energies of the individual phases were obtained.The interdiffusion coefficient for each intermediate phase was calculated by the method introduced by Heumann, and the values obtained were consistent with those derived from Kidson’s equation for the δ, ζ2 and η2 phases.Aluminum oxide powder was used for the measurement of the Kirkendall effect. It is clear from this measurement that diffusion in the multilayer system is controlled by the vacancy mechanism and that aluminum diffuses more rapidly than copper.