Growth behavior of intermetallic compounds in Fe/Sn diffusion couples

In this work, Fe/Sn diffusion couples were manufactured to study the growth behavior and kinetic parameters of intermetallic compounds (IMCs). The diffusion couples were aged at four temperatures, namely at T = 300, 350, 400, and 500 °C, for various times up to 14,400 s. EPMA and XRD were carried out to study the Fe/Sn interface. The layer of IMCs consisted of only FeSn₂ with an irregular microstructure. The growth of IMC layer predominantly took place in the Sn specimen. The mean thickness of the layer was proportional to the power function of the aging time. The growth exponent was close to 0.5 at T = 400 and 500 °C, taking values of 0.479 and 0.503, respectively. Hence, the volume diffusion was the rate-controlling process for the layer growth of IMCs at 400–500 °C. The growth exponent was equal to 0.422 at T = 350 °C and 0.406 at T = 300 °C. Herein, the grain boundary diffusion and volume diffusion contributed to the rate-controlling process. The growth rate constant, K₀, was 3.114 × 10⁻¹⁰ m² s⁻¹ and activation energy was 46.76 kJ mol⁻¹. A mathematical model was established to predict the thickness of IMCs layer as a function of aging time and aging temperature by using Arrhenius equation and including a growth correction factor, y_coor. The prediction results were consistent with the experimental results.