Partition of silicon during eutectic solidification of iron–carbon–silicon alloy

Abstract

The zone-melting technique was used for measuring the effective partition coefficients for silicon between eutectic liquid and its solid during the eutectic solidification following the stable and metastable iron-carbon systems at zone-travelling velocities of less than 2 × 10⁻³ cm s⁻¹. From the measured effective partition coefficients, the equilibrium partition coefficients for silicon in the stable eutectic system k₀ and in the metastable eutectic system k₀′ were calculated to be 1.73 and 0.77, respectively. Furthermore, it was suggested that the boundary layer at a solid/liquid interface during the stable eutectic solidification was 1.6 times as thick as that during the metastable eutectic solidification and that the diffusion coefficient for silicon in iron–carbon eutectic liquid amounted to 1.9 × 10⁻⁵ cm² s⁻¹ at the eutectic temperature. Using thermodynamic data; the equilibrium partition coefficients were also evaluated and were given as k₀ = 1.70–0.31wt-%Si+0.05wt-%Si² and k₀′ = 0.88–0.05wt-%Si. The calculated values were in good agreement with the measured values, and thus the thermodynamic evaluation was useful in the determination of partition coefficients.