| The growth kinetics of intermediate aluminide compound was studied by applying process at temperature range of 700℃-800℃. The intermediate phase observed was confirmed to be Fe₂Al_5 (η) phase whose growth obeyed a parabolic rate law. Growth of intermeditate phase depends on interdiffusion of iron and aluminum. And chemical diffusion coefficients of Al and Fe in η phase are obtained through the consideration of flux and compound stoichiometry in association of alloy layer growth rate. The addition of silicon to aluminum bath results in decreasing growth rate of the intermediate phase. This effect found to be due to the drastic. reduction of frequency factor. The activation energy for the growth of Fe₂Al_5 (η) was found to be 31㎉/㏖, when specimen was dipped in pure aluminum bath, but activation energy was found to be 24.4㎉/㏖, 16.9㎉/㏖, 18.4㎉/㏖ respectively when dipped in 4%, 8%, 12% Si alloyed aluminum bath. A diffusion study of Fe-Al binary system yielded the interdiffusion coefficients and the activation energy for interdiffusion in the intermediate aluminide, η phase. The growth rate of this phase was retarded by the silicon addition. The silicon addition lowers the activation energy for interdiffusion, but decreases the frequency factor drastically. |
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