Kinetic interactions between solid iron and molten aluminium

In order to improve the metallurgical bond between ferrous inserts and aluminium matrix in castings, the interaction between molten aluminium and solid iron is studied by immersion tests. Morphology evolution and growth kinetics of the intermetallic layers Fe2Al5 and FeAl3 were established as a function of time and temperature. For medium interaction time (<45 min), a diffusion regime controlled the Fe2Al5 growth, while FeAl3 grew under a kinetic regime. The apparent activation energy was evaluated in the range of 700–900 °C for the diffusional growth of the Fe2Al5 layer. A theoretical approach based on a reaction diffusion model of simultaneous growth of the two intermetallic layers was successfully used to describe growth kinetics. The parabolic and linear rate constants of Fe2Al5 and FeAl3 were identified. This approach rationalizes the experiments.