High-temperature viscosity and structure studies of Fe–Si melts based on molecular dynamics simulation

In this study, Fe-xSi (x = 0, 1.5, 3.0, 4.5, 6.5 wt.%) alloys have been investigated using molecular dynamics techniques at 1873 K. The correlation between local atomic structure and viscosity was analyzed at the atomic level. The result demonstrates that the melt viscosity decreases monotonically from 5.71 mPa·s to 5.09 mPa·s as the Si content rises. Further analysis of the radial distribution function (RDF), coordination number (CN), chemical short-range order (CSRO) parameter, Voronoi polyhedra, cluster behavior, and mean square displacement (MSD) reveals that the strong interaction between Si and Fe atoms in the high-temperature liquid phase leads to the decomposition of medium-sized clusters and the formation of small atomic clusters in the original system. This results in a decrease in coordination number, a reduction in the total number and size of clusters, and an increase in the proportion of free volume. Therefore, atomic diffusion inside the melt becomes more significant, and the order degree of the internal network structure of the melt decreases, thereby reducing the melt viscosity. These findings provide important insights into the structure-transport property relationship of liquid alloys and offer theoretical guidance for improving the planar flow casting process of silicon steel strips.