Evolution of Al2O3 inclusions by cerium treatment in low carbon high manganese steel

The influence of cerium (Ce) treatment on the morphologies, size and distributions of Al2O3 inclusions in low carbon high manganese steel was investigated by OM, SEM-EDS and theoretical calculation. The results showed that Ce can modify the morphologies and types of Al2O3 inclusions. After Ce treatment, the irregular Al2O3 inclusions were replaced by smaller and dispersive spherical cerium oxysulfides. The effects of treatment time and Ce content on the evolution of Al2O3 inclusions were examined. It indicated that Al2O3 inclusions were wrapped by rare earth inclusions to form a ring like shape Ce-enriched band around the inclusions. Model was established to elucidate the evolution mechanism of Al2O3 inclusions. Evolution kinetics of inclusions was discussed qualitatively to analyze the velocity controlled step. It was found that diffusion of Ce3+ and Al3+ in solid inclusion core and the formed intermediate layer would be the limited step during the evolution process.