Study on the growth and morphology evolution of titanium oxide clusters in molten iron with molecular dynamics simulation

New Insights into the Mechanism of Nucleation of ZrO2 Inclusions at High Temperature

It is difficult to observe the nucleation mechanism of inclusions in real-time. In this study, the nucleation process of zirconium oxide inclusions was systematically studied by classical nucleation theory and first principles. Zr deoxidized steel with 100 ppm Zr addition was processed into metallographic samples for scanning electron microscopy energy-dispersive spectroscopy observation. The electrolytic sample was analyzed by micro X-ray diffraction and transmission electron microscopy, and the zirconium oxide in the sample was determined to be ZrO₂. The nucleation rate and radius of the ZrO₂ inclusions were calculated by classical nucleation theory, and they were compared with the experimental values. There was a considerable difference between the experimental and theoretical values of the nucleation rate. The effect of the nucleation size was analyzed by first-principles calculation, and the thermodynamic properties of ZrO₂ clusters and nanoparticles were analyzed by constructing (ZrO₂)_n (n = 1-6) clusters. The thermodynamic properties of ZrO₂ calculated by first principles were consistent with the values in the literature. Based on two-step nucleation theory, the nucleation pathway of ZrO₂ is as follows: Zr_atom + O_atom → (ZrO₂)_n → (ZrO₂)₂ → core (ZrO₂ particle)-shell ((ZrO₂)₂ cluster) nanoparticle → (ZrO₂)_bulk.