Thermodynamic and Crystallographic Analysis on Complex Inclusions in Ti Deoxidized Low Carbon Steel

Complex inclusions can be successfully separated from matrix in the steel by means of carbon replica method. The complex morphology became visible using transmission electron microscope (TEM) and the chemical composition turned into knowable by energy dispersive spectroscopy (EDS). The structure of inclusions can be determined by collecting diffraction patterns. Precipitation sequence can be estimated via complex morphology which present that as the melt cooling down, TiO₂ nucleation first, and then Fe₂SiO₄ grow on it. In addition, MnS precipitated on the outermost layer of the complex inclusions. Thermodynamic calculations can describe the precipitation situation of complex inclusions and crystallography analysis can explain its mismatch condition and orientation relationship. These results show good agreement with the experiment. Based on the results, we can optimize the material compositions and cooling rate to modify the precipitation size and morphology, which can refine the grains and improve the performance of low carbon steel.