The Nucleation Potency of In Situ-Formed Oxides in Liquid Iron

Abstract

The nucleation potency of iron oxides was verified experimentally through nucleation undercooling of liquid iron using aerodynamic levitation technology for minimized container contaminations. Steady undercooling values were subsequently obtained from multiple melting and freezing thermal cycles, with the average undercooling values of 223 K ± 3 K and 75 K ± 6 K (223 °C ± 3 °C and 75 °C ± 6 °C) for FeO-contained liquid and Fe₃O₄-contained liquid, respectively. The statistical results showed a negligible difference in the sizes and numbers of particles between FeO and Fe₃O₄ particles, indicating that the nucleation potency difference is attributed to the nature of nucleants rather than particle size or numbers. Furthermore, high-resolution transmission electron microscopy analysis showed that the potential nucleation interfaces can be assumed as $\{ 1 1 0\}_{{\delta {\text{{-}Fe}}}} //( 0 0\bar{2})_{\text{FeO}}$ and $\{ 1 1 2\}_{{\delta {\text{{-}Fe}}}} //(\bar{2} 0 2 )_{{{\text{Fe}}_{3} {\text{O}}_{4} }}$, based on the detected exposed crystal planes of the oxide particles. Both the interfaces have relatively large values of lattice misfit, consistent with the experimentally measured undercooling based on Turnbull’s lattice matching theory.